Add tests for the main code paths in `Guest` that call `createAnnotation`.

Convert the `createAnnotation` method of `Guest` to use async/await
instead of manual chaining of Promise operations. This makes it easier
to follow the logic and see that document metadata is assigned to the
annotation before it is broadcast to other parts of the annotator in the
`beforeAnnotationCreated` event. It also makes it easier to external
code (eg. the tests) to determine when `createAnnotation` is "done" and
has finished updating the annotation.

 - Convert `Guest#createAnnotation` to use async/await

 - Update tests for `createAnnotation` to await the returned Promise
   instead of a fixed timeout

 - Add a missing check in `createAnnotation` tests for the argument
   passed to the `beforeAnnotationCreated` event

Open links to documents in a new tab. This is important in the Notebook
view at present to "escape" the Notebook's frame, but makes sense in
all contexts as it more closely adheres to our pattern of opening links
to external properties in new windows.

Make sure document titles that are not linked don't look like links.

Make `AnnotationTimestamps` align with changes to `ShowDocumentInfo`;
it is now a dumb component. Centralize logic in `AnnotationHeader`.

- Refactor `ShowDocumentInfo`: don't link to documents for third-party
  annotations. This is a possibly-temporary measure to prevent linking
  to documents that are not directly accessible, e.g. in an LMS context.
- Remove unnecessary forwarding of `showDocumentInfo` through several
  components.
- Centralize some logic in `AnnotationHeader` and make `ShowDocumentInfo`
  a dumb component.

These changes enforce that the bucket-bar is destroyed and allows
multiple creations of the bucket bar, if needed.

The sidebar is not the only other frame that may be interested in new
annotations. The notebook is too.

 - Extract the repeated logic for checking the data passed to the
   event's callback into a `createCallback` helper

 - Add separate tests for HTML and PDF documents

 - Add test for the error path when getting the URL of a PDF fails

Replace the "plugin" functionality in the Guest that indirectly
instantiates the `DocumentMeta`, `PDF` and `CrossFrame` classes with
direct instantiation of those classes.

The annotator part of the Hypothesis client is no longer a pluggable
toolbox which can be arbitrarily extended by user-provided plugins.
Removing the "plugins" logic and replacing it with direct construction
of the necessary classes removes a lot of indirection that made the code
harder to follow and also makes it easier for TypeScript to statically
check the code. It will also enable the `config` object that is passed
to `Guest` to be paired down to just the fields that are actually needed
and properly typed.

In future we will need some kind of plugin/integration facility to
support different document viewers. For we will build a more specific
document type integration facility when the time comes.

 - Remove `this.plugins` field from `Guest` class and `pluginClasses`
   config and replace with direct construction of `PDFIntegration`,
   `DocumentMeta` and `CrossFrame` classes

 - Update the `AnchoringImpl` typedef to correctly reflect that some anchoring
   implementations (HTML) have a synchronous `describe` method

 - Remove unnecessary `config` argument to `PDF` constructor

 - Replace the `PDF: {}` content in the guest config with `documentType:
   'pdf'` as a more obvious way for the annotator entry point to
   configure which document viewer integration is loaded. In future we
   can generalize this to support different types of viewer integration.

This PR prevents scrolling of the body of the host when the notebook is
opened.

Reported
[here](https://github.com/hypothesis/client/pull/3024#pullrequestreview-592240569).

This solution doesn't work for iOS < 13.

- made the button stick on the top without taking space from the
  notebook. I re-enabled the original padding of the notebook.

- fixed an issue with window resizing that caused the notebook to
  disappear.

- on touch devices closing the notebook, closed the sidebar too.

The sidebar component directs the opening of the notebook. This is for two reasons:

* it's a little bit easier to save the UI state of the current sidebar
  (immediately before the notebook is opened), in case in the future we
  want to restored it.

* to avoid adding additional events, like `show/hideSidebarControls`,
  that probably would be needed for granular control of the sidebar, in
  case the notebook would be directing the process of closing/re-opening
  the sidebar.

Because I am planning to introduce another method to hide the controls,
I renamed the hide/show methods in the sidebar and notebook components
to open/close. I also feel it describes better the visual outcome.

For consistency, I renamed the show/hideNotebook to open/closeNotebook.

Render the bucket bar immediately using the Guest's current set of anchors when it
is constructed.

This resolves an issue introduced in 68d44395 that the background of the
bucket bar did not appear until after the first batch of annotations had
been fetched from the API and synced from the sidebar to the annotator.
It also ensures that buckets are drawn for any anchors that already
exist in the Guest when the BucketBar is initialized.

 - Move `annotator-bucket-bar-width` variable down into the one file
   that uses it
 - Remove unused `annotator-bucket-bar-line-height` variable

Rename CSS classes used by the bucket bar to match the `Buckets`
component name and move the corresponding styles into
src/styles/annotator/components/Buckets.scss.

As was recently done with the sidebar's vertical toolbar, the styles on the bucket bar
container were moved to an element rendered by the `Buckets` component
itself, so that there is a 1:1 association between JS modules and SASS
modules for the bucket bar.

Bumps [@babel/preset-env](https://github.com/babel/babel/tree/HEAD/packages/babel-preset-env) from 7.13.8 to 7.13.9.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/main/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/commits/v7.13.9/packages/babel-preset-env)
Signed-off-by: dependabot[bot] <support@github.com>

Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.853.0 to 2.854.0.
- [Release notes](https://github.com/aws/aws-sdk-js/releases)
- [Changelog](https://github.com/aws/aws-sdk-js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/aws/aws-sdk-js/compare/v2.853.0...v2.854.0)
Signed-off-by: dependabot[bot] <support@github.com>

Bumps [@octokit/rest](https://github.com/octokit/rest.js) from 18.3.0 to 18.3.1.
- [Release notes](https://github.com/octokit/rest.js/releases)
- [Commits](https://github.com/octokit/rest.js/compare/v18.3.0...v18.3.1)
Signed-off-by: dependabot[bot] <support@github.com>

Bumps [@sentry/browser](https://github.com/getsentry/sentry-javascript) from 6.2.0 to 6.2.1.
- [Release notes](https://github.com/getsentry/sentry-javascript/releases)
- [Changelog](https://github.com/getsentry/sentry-javascript/blob/master/CHANGELOG.md)
- [Commits](https://github.com/getsentry/sentry-javascript/compare/6.2.0...6.2.1)
Signed-off-by: dependabot[bot] <support@github.com>

Bumps [chai](https://github.com/chaijs/chai) from 4.3.0 to 4.3.1.
- [Release notes](https://github.com/chaijs/chai/releases)
- [Changelog](https://github.com/chaijs/chai/blob/main/History.md)
- [Commits](https://github.com/chaijs/chai/compare/4.3.0...4.3.1)
Signed-off-by: dependabot[bot] <support@github.com>

- Remove github actions related to frontend-shared
- Remove scripts and gulp commands related to frontend-shared
- frontend-shared is now managed from its own repository.

There was a version issue between the current installed version 1.4.0 and the local copy being using in the subfolder (/frontend-shared). The newest shared package exports an _index.scss file which is required by the client, but it was not formally importing a version of the shared package which exported the _index.scss file. The client now imports 1.9.0 which has _index.scss and now the frontend-shared folder can be fully removed from the client.

TL;DR, This is just more reason to move the shared package to its own repo because this issue was being masked.

Fix a regression introduced in b52f00e0 where clicking in a PDF
when side-by-side is active would cause the sidebar to close instead of
remaining open. That PR made `PdfSidebar` no longer inherit (indirectly)
from Guest but did not update the references to the `closeSidebarOnDocumentClick`
property of the Guest.

This handler sets the `document` property of new annotations to metadata
extracted from `<meta>` and `<link>` tags on the page. It is unnecessary
however because the `Guest` class sets this property using either
`DocumentMeta.metadata` or `PDF.getMetadata`, depending on the document
type, before it emits the `beforeAnnotationCreated` event.

In PDFs this code is a serious hazard because if the
`beforeAnnotationCreated` event subscriber in `DocumentMeta` runs before
`AnnotationSync`'s corresponding event handler then DocumentMeta will
overwrite the PDF document-specific annotation metadata with generic
HTML document metadata - losing the critical `documentFingerprint`
property. Fortunately this problem did not occur because the `Guest`
constructor instantiates the `AnnotationSync` class before the
`DocumentMeta` class. Consequently AnnotationSync's
`beforeAnnotationCreated` event handler runs before DocumentMeta's and
pushes new annotations to the sidebar with the correct document metadata
before `DocumentMeta` overwrites it.

The ThreadList component has a required felid  `threads` but its value was undefined in tests. The value comes from the mocked version of `useRootThread.children`

The recent refactor to change the relationship between the `Guest` and `Sidebar`
classes broke PDF.js integration because the `PdfSidebar` class is no
longer able to modify the config that is passed to the `Guest` class.
Previously it would pass `PDF: {}` in the config to the `super()` call
which would then result in the `Guest` class loading the PDF
integration.

This now has to be done in the `index.js` module. We already had to do
this previously for ebooks. Now it has to be done for all scenarios.

If `make sure` or `make checkformatting` are the first command that are
run after version update that included prettier, the commands will use
the previous version of prettier.

With the recent changes in the gulp test command (#2989), everything
that could be achieved by `make servetest` can be done by options to the
`make test` target.

Removed @ts-ignore

Bumps [typescript](https://github.com/Microsoft/TypeScript) from 4.1.5 to 4.2.2.
- [Release notes](https://github.com/Microsoft/TypeScript/releases)
- [Commits](https://github.com/Microsoft/TypeScript/compare/v4.1.5...v4.2.2)
Signed-off-by: dependabot[bot] <support@github.com>

The `guest` argument is required but the `config` argument is now
optional. Swap them so that required arguments come before optional
ones and set a default value for `config`.

Change the relationship between the `Guest` and `Sidebar` classes from
one of inheritance to one where `Sidebar` receives a reference to the
`Guest` instance and calls methods on it or subscribes to events from
it. The `Guest` also no longer "owns" references to the bucket bar /
toolbar objects that logically belong to the sidebar. Instead it emits
events which the sidebar responds to.

This change makes the interface of the `Guest` used by the `Sidebar`
more explicit and ensures a better boundary between the two. This also
makes it easier for the `Sidebar` tests to be concerned only with the
interface of the `Guest` and not its implementation details. In future
this change will also make it possible to have a frame which does not
contain a sidebar but is not annotateable. We had a need for this
historically when integrating with epub viewers, although it was never
implemented.

Updating the tests for `PdfSidebar` was complicated by the fact that the
`PdfSidebar` tests are not pure unit tests. They instantiate the
`Sidebar` base class and so depend on many implementation details of it.
To make this change and others easier, the `PdfSidebar` tests have been
changed to mock the `Sidebar` base class. The steps involved in this are
non-obvious so I extracted the logic into a utility function.

 - Change `Sidebar` to no longer inherit `Guest` but accept it as a
   constructor argument
 - Remove direct references to the `BucketBar` and `ToolbarController`
   instances from the `Guest` class and instead emit events from the
   `Guest` which the `Sidebar` responds to.
 - Add a `mockBaseClass` testing helper in `src/test-util/mock-base.js`
   and change the `PdfSidebar` tests to use it, so that they are less
   coupled to `Sidebar` implementation details.

Bumps [@babel/core](https://github.com/babel/babel/tree/HEAD/packages/babel-core) from 7.12.17 to 7.13.8.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/main/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/commits/v7.13.8/packages/babel-core)
Signed-off-by: dependabot[bot] <support@github.com>

Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.848.0 to 2.853.0.
- [Release notes](https://github.com/aws/aws-sdk-js/releases)
- [Changelog](https://github.com/aws/aws-sdk-js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/aws/aws-sdk-js/compare/v2.848.0...v2.853.0)
Signed-off-by: dependabot[bot] <support@github.com>

Bumps [@babel/preset-env](https://github.com/babel/babel/tree/HEAD/packages/babel-preset-env) from 7.12.17 to 7.13.8.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/main/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/commits/v7.13.8/packages/babel-preset-env)
Signed-off-by: dependabot[bot] <support@github.com>