Core: Namespace sidebar config options

[ghengeveld]

Issue: -

What I did

This deprecates showRoots in favor of sidebar.showRoots, moves the recently introduced collapsedRoots (beta) to be under sidebar as well and removes sidebarAnimations altogether.

Should we show a deprecation warning for sidebarAnimations as well? It's not going to break, but people may want to clean up their config.

How to test

• Is this testable with Jest or Chromatic screenshots? Yes, nothing should change
• Does this need a new example in the kitchen sink apps? No
• Does this need an update to the documentation? Yes, it's there

If your answer is yes to any of these, please make sure to include it in your PR.

[github-actions]

	Fails
🚫	Please choose only one of these labels: ["documentation","maintenance"]

Generated by 🚫 dangerJS against c263d1d

[shilman]

This is great @ghengeveld -- thanks for cleaning up 🙏

[nhoizey]

I lost a few minutes trying to find the documentation for sidebarAnimations I had in a project, so I would vote for a deprecation warning and at leat a mention in MIGRATION.md