[Discover] Migrate discover.html Angular template to React

[kertal]

Summary

This PR removes the Angular template discover.html, converts it into DiscoverLegacy.tsx, a React component. Discover's doc table is still in Angular, so this is also converted into a React Component DocTableLegacy, that's a wrapper for an Angular directive. So we're basically turn the table. Before, it was React in Angular, now it's Angular in React. This enables us to continue deangularization (controller, embeddable, router) without being blocked by the one indomitable gallic village of Angular in a React occupied plugin.

Checklist

Delete any items that are not applicable to this PR.

• Unit or functional tests were updated or added to match the most common scenarios

[kertal]

@kertal Is this ready to be reviewed again?

@flash1293 yes, if Jenkins goes green 🌲 🍏 💚

[flash1293]

Tested in Chrome and Firefox and didn't notice any issues. Looks good to me once the aria-expanded I commented on is fixed

[snide]

Naming issue on the scss.

[cchaos]

There's still a few seemingly arbitrary pixel values in the SASS, but I'll 👍 for now to unblock progress.

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 31cf12f

Build metrics

@kbn/optimizer bundle module count

id	value	diff	baseline
discover	256	-3	259

async chunks size

id	value	diff	baseline
discover	438.3KB	+7.1KB	431.2KB

page load bundle size

id	value	diff	baseline
discover	230.0KB	+104.0B	229.9KB

History

• 💚 Build #74695 succeeded e79be95
• 💚 Build #74441 succeeded 101ff24
• 💚 Build #74109 succeeded ee43b9e
• 💔 Build #74099 failed a59fafc
• 💚 Build #74016 succeeded 8011988

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@elasticmachine merge upstream