Revise re-fetching of groups when logged-in user changes

Use the dummy/blank profile object as the initial value of the `profile`
field rather than `null`. This allows us to eliminate null-checks
elsewhere while still enabling `hasFetchedProfile` to distinguish this
profile from the profile fetched from the API.

Add visibility hidden to the sidebar iframe when its closed (and after it finishes animation). This prevents all interaction from the components of the sidebar.

Add an optional coerce method to the hostPageSetting so that any incoming values can be coerced if needed. This may be required for values from from via that may only be a string type.

openSidebar config value gets coerced to a boolean in the annotator settings (just like it does in the host-config).

Redo the automatic reload of groups when the logged-in user changes:

 - Ignore the initial change of user on startup if the user is logged
   in from a previous session. This generated an unnecessary additional
   API call on startup if the user had a login from a previous session

 - Replace the use of the deprecated `USER_CHANGED` Angular event in
   favor of reacting to store state changes using
   `watch(store.subscribe, ...)`

Change the representation of the un-fetched profile within the `session`
store module to make it possible to determine whether the profile has
been fetched yet or not and expose this information via a
`hasFetchedProfile` selector. The `profile` selector continues to return
a dummy "logged out" profile before the real profile is fetched. This
simplifies some of the code that uses that selector.

This makes it possible for services to distinguish between the user ID changing
because the user logged in by clicking "Log in" and completed the login
process vs. the user already being logged in from a previous session.

Replace remaining uses angular-toastr/flash with toastMessenger

Per Lyza's suggestion and matches the examples at
https://www.typescriptlang.org/docs/handbook/type-checking-javascript-files.html

Remove unused Preact component wrappers

Fix thread list jumping when scrolling on mobile

Bump commander from 5.0.0 to 5.1.0

Bump sass from 1.26.3 to 1.26.5

Bumps [dompurify](https://github.com/cure53/DOMPurify) from 2.0.9 to 2.0.10.
- [Release notes](https://github.com/cure53/DOMPurify/releases)
- [Commits](https://github.com/cure53/DOMPurify/compare/2.0.9...2.0.10)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bump mocha from 7.0.1 to 7.1.2

Bumps [commander](https://github.com/tj/commander.js) from 5.0.0 to 5.1.0.
- [Release notes](https://github.com/tj/commander.js/releases)
- [Changelog](https://github.com/tj/commander.js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/tj/commander.js/compare/v5.0.0...v5.1.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bump terser from 4.6.11 to 4.6.12

Remove old toast notifications UI and dependencies as these are no
longer used.

For certain error messages, we do not want the notice to be dismissed
automatically as either the issue prevents further usage of the client
(eg. a problem acquiring an access token when third-party accounts are
in use) or the problem is likely to happen while the user is not
interacting with the client.

Add an `autoDismiss` option to `toastMessenger` message methods and use
it when handling access token fetching errors on pages that use
third-party accounts.

Toasts in the old UI used to have a title and a message. Toasts in the
new UI currently only have a message.

Replace the last remaining uses of the old toast notification service
and UI (`flash`) with the new one (`toastMessenger`). This provides a
better-looking and accessible experience for these errors.

Work around issue with Node v14 and Puppeteer

Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.660.0 to 2.663.0.
- [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/v2.660.0...v2.663.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Use the system version of Chrome if the developer has Node v14
installed, to work around an upstream issue with Puppeteer (see code
comment).

Bumps [terser](https://github.com/terser/terser) from 4.6.11 to 4.6.12.
- [Release notes](https://github.com/terser/terser/releases)
- [Changelog](https://github.com/terser/terser/blob/master/CHANGELOG.md)
- [Commits](https://github.com/terser/terser/compare/v4.6.11...v4.6.12)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@octokit/rest](https://github.com/octokit/rest.js) from 17.5.1 to 17.6.0.
- [Release notes](https://github.com/octokit/rest.js/releases)
- [Commits](https://github.com/octokit/rest.js/compare/v17.5.1...v17.6.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [mocha](https://github.com/mochajs/mocha) from 7.0.1 to 7.1.2.
- [Release notes](https://github.com/mochajs/mocha/releases)
- [Changelog](https://github.com/mochajs/mocha/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mochajs/mocha/compare/v7.0.1...v7.1.2)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [sass](https://github.com/sass/dart-sass) from 1.26.3 to 1.26.5.
- [Release notes](https://github.com/sass/dart-sass/releases)
- [Changelog](https://github.com/sass/dart-sass/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sass/dart-sass/compare/1.26.3...1.26.5)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bump karma-mocha from 1.3.0 to 2.0.0

Remove some Angular wrappers for Preact components which are no longer
needed.

Re-measurement of the height of visible threads happened in an effect
that depended only on the set of top-level threads, not the subset that
were currently visible.

On desktop, hover events would cause annotations to be focused as the
user scrolled through the list, resulting in the root thread being
recalculated regularly and hence the internal `threadHeights` state in
`ThreadList` was usually accurate.

On mobile however, hover events don't fire and therefore `threadHeights` was
not updated as often as it should be. The mismatch between the actual
rendered height of threads and the value in `threadHeights` caused the
thread list to jump as a thread above the viewport was transitioned from a
rendered to a non-rendered state. This issue can be reproduced in Chrome
on desktop when the device type is set to "Mobile (Touch)" in dev tools.

This PR fixes the issue by making recalculation depend on the set of
_visible_ threads. In practice `visibleThreads` changes on most renders,
however the amount of work the effect does if no measured heights
changed is small, so this shouldn't be an issue.

In addition to fixing this issue, this commit also adds a test for the
overall behavior as the user scrolls through the list. Since correct
behavior depends on complex interaction between the DOM, `ThreadList`
and logic in two utility modules, we avoid mocking either the DOM or
utilities in these tests.

Convert stream content to Preact

This is a fairly direct conversion of the `<stream-content>` component
from AngularJS to Preact.

There is one minor improvement which is to display an error notification
if fetching annotations from the API fails.

Convert single annotation page content to Preact

- Allow keyboard navigation of menus
- Fix various menu a11y issues
- Fix one underlying issue where executing a link in the menu with keyboard (Enter or Space) never worked
- Add MenuKeyboardNavigation helper component

Bump aws-sdk from 2.658.0 to 2.660.0