K7 Discover app cleanup

[snide]

Summary

cc @cchaos @Bargs @lukasolson for awareness

Some quickie cleanup for the discover app

TODO

• fix some accessibility stuff caused by the hover states
• I'll also need to do cleanup of the surround document pages
• hunt down an errant horizontal scrollbar

Doc table rows decluttered

I removed all the repetitive icons and bordering. Now the action buttons show up on hover. I also did an angular .euiTab fakeout because those bootstrap tabs were hideous.

Cleanup of filter bar and index selector

Just a bunch of minor cleanup to fix the popover dropdowns, spacing and sizing of these elements.

Sidebar cleanup

Cleaned up the sidebar to be less aggressive. Will likely do a similar cleanup to repetitive icons here.

Fixed obvious dark mode breaks

Checklist

Use strikethroughs to remove checklist items you don't feel are applicable to this PR.

• This was checked for cross-browser compatibility, including a check against IE11
• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• This was checked for keyboard-only and screenreader accessibility

For maintainers

• This was checked for breaking API changes and was labeled appropriately
• This includes a feature addition or change that requires a release note and was labeled appropriately

[elasticmachine]

Pinging @elastic/kibana-design

[elasticmachine]

💔 Build Failed

• continuous-integration/kibana-ci/pull-request

[elasticmachine]

💔 Build Failed

• continuous-integration/kibana-ci/pull-request

[snide]

retest

[elasticmachine]

💔 Build Failed

• continuous-integration/kibana-ci/pull-request

[elasticmachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request

[snide]

Yay. With a little over an hour to spare :)

@cchaos if you have time in the morning. feel free to do a quick review. I also fixed a dark mode issue with the kibana loader.

[cchaos]

LGTM!