[Canvas] K7 design related fixes

[ryankeairns]

Fixes #30711 #30333 #30735

Summary

Fixes a few design related issues in the K7 theme:

• removes white space (on left hand side) in fullscreen mode
• reduces the font size within Canvas chrome areas (i.e. header and footer buttons, sidebar tabs)
• makes 'Canvas is loading' text lighter on loading screen

Screenshots

Fullscreen has black background to left edge

Canvas chrome font size is 14px

Loading screen has lighter font color in dark mode

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 (checked in IE11, Kibana wouldn't load in Edge)
• 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](https://developer.mozilla.org/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Accessibility#Accessibility_testing_checklist)

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]

💚 Build Succeeded

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

[alexfrancoeur]

@ryankeairns is this good for review or were you making anymore changes?

[ryankeairns]

@alexfrancoeur it is ready for review.

Note on font sizes: I set the menu bar (above the workpad), toolbar (below the workpad), and tabs in the sidebar all to 14px (smaller). Beyond that, I'd like to do a broader comparison across K7 as things settle down before making blanket typography changes to other labels, titles, etc.

For example, there is work ongoing in the new Viz builder and in Maps, both of which also have sidebars, so it would be good to compare and work towards consistency.

Thanks!

[snide]

Did a code review only. LGTM.

[cchaos]

@ryankeairns Can you do one more thing that's been bugging me? Can you remove the compressed prop from the canvas workpad listing table? The text is sooo tiny but it's the primary list. And just looks so small now against the table controls.

[elasticmachine]

Pinging @elastic/kibana-canvas

[elasticmachine]

💚 Build Succeeded

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

[monfera]

Nice changes! A small commit with the top/left unification would be neat before the merge

[elasticmachine]

💚 Build Succeeded

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