Add new preact tag editor component

Add and use new `IconButton` component

Add and use new `ActionButton` component

No longer needed after `IconButton` added

- Eliminate custom sub-components that fulfill the same task
- Replace `AnnotationActionButton` with `IconButton` where used
- Consolidate and adjust styling

Bump scroll-into-view from 1.12.3 to 1.13.1

Bump fetch-mock from 8.0.1 to 8.1.0

Bump npm-packlist from 2.0.1 to 2.0.2

Bumps [fetch-mock](https://github.com/wheresrhys/fetch-mock) from 8.0.1 to 8.1.0.
- [Release notes](https://github.com/wheresrhys/fetch-mock/releases)
- [Commits](https://github.com/wheresrhys/fetch-mock/compare/v8.0.1...v8.1.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [npm-packlist](https://github.com/npm/npm-packlist) from 2.0.1 to 2.0.2.
- [Release notes](https://github.com/npm/npm-packlist/releases)
- [Commits](https://github.com/npm/npm-packlist/compare/v2.0.1...v2.0.2)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [scroll-into-view](https://github.com/KoryNunn/scroll-into-view) from 1.12.3 to 1.13.1.
- [Release notes](https://github.com/KoryNunn/scroll-into-view/releases)
- [Commits](https://github.com/KoryNunn/scroll-into-view/commits)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.586.0 to 2.590.0.
- [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/v2.586.0...v2.590.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@octokit/rest](https://github.com/octokit/rest.js) from 16.35.0 to 16.35.2.
- [Release notes](https://github.com/octokit/rest.js/releases)
- [Commits](https://github.com/octokit/rest.js/compare/v16.35.0...v16.35.2)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Fix naming inconsistency of modules in src/sidebar/util

Fix a naming inconsistency for modules in src/sidebar/util where some
had a `-util` suffix and some did not.

Consolidate some form and button styles

In advance of some migration work, remove some unused classes, extract
some color variables and organize.

Update Cancel UI for `AnnotationPublishControl`

Don't filter annotations when showing "All Students"

When the client is running in the LMS app and in grading mode, don't
apply a broken filter to the annotations list when the LMS app is asking
the client to show "All Students".

Fixes https://github.com/hypothesis/lms/issues/1259

The LMS app sends username not userid:

https://github.com/hypothesis/lms/blob/d6b88fd7e375a4b23899117556b3e39cfe18986b/lms/static/scripts/frontend_apps/components/LMSGrader.js#L36

But the test for ths client code that receives this was sending
userid.

Fix the test to send username, the same as the LMS app does.

Consolidate all grey colors across client application

Migrate usages of `$gray-light` to `$grey-semi`

Migrate usages to `$grey-5`

Introduce a new color variable, `$grey-mid`, which sits between
`$color-5` and `$color-6` in the current palette scale and fills a
large gap.

Remove `$gray-dark` and `$color-dove-gray` after migrating to `$grey-mid`.

Migrate single usage to `$grey-5`

Migrate all usages to `$grey-6` (close approximate).

Migrate `$gray-lighter` SASS color to `$grey-3`

`$gray-lighter` is deprecated. Its color value (#d3d3d3) is close enough
to `$grey-3` (#dbdbdb) to make a simple substitution feasible.

Remove unused styles referencing `$gray-lighter`

Update core-js to current version

Replace deprecated gulp-util dependency

Bump @sentry/browser from 5.10.1 to 5.10.2

Bump preact from 10.0.5 to 10.1.0