WIP: Fix examples color theme system

[jmuzina]

Done

Vanilla's example components have color theme pickers to help users view components in different color themes, however the color theme picker has some usability problems as-is:

• The "selected" color theme is not shown on the theme picker. So the only way to tell which theme is selected is to guess or to click buttons until you find the active theme.
• Some examples (such as Suru) have theme options for themes they do not support. For example, Suru only supports Paper & Dark, but the example page has an option for light (clicking this button does not do anything). This is confusing, and it also leads to a question of listing which components support which themes for maintainability reasons.

This PR makes the theme picker reflect the state of the example component, and only reflect the themes that are supported for the component.

Further, the color theme switcher has been changed to use the Segmented Control component as it is a better fit for our use case.

Fixes:

• WD-11110
• Examples theme picker does not reflect selected theme #5069

Color theme selection rules

(diagram / explanation WIP)

QA

• Open demo
• [Add QA steps]
• Review updated documentation:
  • [List any updated documentation for review]

Check if PR is ready for release

If this PR contains Vanilla SCSS code changes, it should contain the following changes to make sure it's ready for the release:

• PR should have one of the following labels to automatically categorise it in release notes:
  • Feature 🎁, Breaking Change 💣, Bug 🐛, Documentation 📝, Maintenance 🔨.
• Vanilla version in package.json should be updated relative to the most recent release, following semver convention:
  • if CSS class names are not changed it can be bugfix relesase (x.x.X)
  • if CSS class names are changed/added/removed it should be minor version (x.X.0)
  • see the wiki for more details
• Any changes to component class names (new patterns, variants, removed or added features) should be listed on the what's new page.

Screenshots

[if relevant, include a screenshot or screen capture]

[webteam-app]

Demo

Jenkins

demos.haus

[jmuzina]

Closed as too-broadly-scoped. Opting for more limited version #5087