Modify a mocking idiom that doesn't work with ES modules

We have an idiom in many tests where we import the "default export" from
a module and then access the `$imports` property on that
function/class/object in order to mock or unmock imports. For example:

```
const Widget = require('../widget');

beforeEach(() => {
  Widget.$imports.$mock(...);
});

afterEach(() => {
  Widget.$imports.$restore();
});
```

This won't work when the module under test is converted to an ES module
because the `$imports` object will become a separate export from the
module rather than a property of the default export.

Move `delete` and `flag` logic into `AnnotationActionBar` sub-component

Move the (straightforward) flag and delete logic into the
AnnotationActionBar component, near to where the UI interaction
takes place to lessen complexity of `Annotation`

Add `isHighlight` util function to `annotation-metadata`

Bump sinon from 8.0.1 to 8.0.2

Bump redux from 4.0.4 to 4.0.5

Bump terser from 4.4.3 to 4.5.1

Bump fetch-mock from 8.3.0 to 8.3.1

Bump sass from 1.23.7 to 1.24.2

Bump mocha from 6.2.2 to 7.0.0

Bump commander from 4.0.1 to 4.1.0

- Add `waitFor` util for easier async testing 

Make Annotation sub-components compute their own privacy

Stop passing result of `Annotation.state.isPrivate` through
`AnnotationActionBar` to `AnnotationShareControl` but instead
have `AnnotationShareControl` compute privacy itself.

Stop passing value of `Annotation.state.isPrivate()` through
`AnnotationHeader` all the way to `AnnotationShareInfo` and
instead compute that within `AnnotationShareInfo` itself.

When tag suggestions exceeds just a few hundred results, a noticeable performance is observed in Chrome.

- Add limit param to services.tags.filter()
- Use filter limit when user agent is Chrome

Complete final sidebar SVG icon conversions

Bumps [redux](https://github.com/reduxjs/redux) from 4.0.4 to 4.0.5.
- [Release notes](https://github.com/reduxjs/redux/releases)
- [Changelog](https://github.com/reduxjs/redux/blob/master/CHANGELOG.md)
- [Commits](https://github.com/reduxjs/redux/compare/v4.0.4...v4.0.5)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@babel/preset-env](https://github.com/babel/babel) from 7.7.6 to 7.7.7.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/compare/v7.7.6...v7.7.7)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [sinon](https://github.com/sinonjs/sinon) from 8.0.1 to 8.0.2.
- [Release notes](https://github.com/sinonjs/sinon/releases)
- [Changelog](https://github.com/sinonjs/sinon/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sinonjs/sinon/compare/v8.0.1...v8.0.2)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [terser](https://github.com/terser/terser) from 4.4.3 to 4.5.1.
- [Release notes](https://github.com/terser/terser/releases)
- [Changelog](https://github.com/terser/terser/blob/master/CHANGELOG.md)
- [Commits](https://github.com/terser/terser/commits)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.595.0 to 2.597.0.
- [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/v2.595.0...v2.597.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [fetch-mock](https://github.com/wheresrhys/fetch-mock) from 8.3.0 to 8.3.1.
- [Release notes](https://github.com/wheresrhys/fetch-mock/releases)
- [Commits](https://github.com/wheresrhys/fetch-mock/compare/v8.3.0...v8.3.1)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [sass](https://github.com/sass/dart-sass) from 1.23.7 to 1.24.2.
- [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/1.23.7...1.24.2)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [mocha](https://github.com/mochajs/mocha) from 6.2.2 to 7.0.0.
- [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/v6.2.2...v7.0.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [eslint](https://github.com/eslint/eslint) from 6.7.2 to 6.8.0.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/master/CHANGELOG.md)
- [Commits](https://github.com/eslint/eslint/compare/v6.7.2...v6.8.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [commander](https://github.com/tj/commander.js) from 4.0.1 to 4.1.0.
- [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/4.0.1...v4.1.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@babel/core](https://github.com/babel/babel) from 7.7.5 to 7.7.7.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/compare/v7.7.5...v7.7.7)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Prepare for transition to ES modules