Animation: Verify behavior and performance

[srambach]

Tie up animation by verifying correct behavior on all components using it:

• Reduced motion works as intended
• Animation timings are correct. For expando/collapso, it's 200ms expand, 100ms collapse
• Add inert to core examples
• Make sure inert is applied to the react components
• We aren't breaking core-only users
• No apparent jankiness with CPU throttling
• Cross-browser behavior is acceptable (progressive enhancement animation ok, but no visual/behavior is broken)
• ... anything else?