[core] fix(PanelStack2): more stable controlled mode

[adidahiya]

Fixes #4807

Checklist

• Includes tests
• Update documentation

Changes proposed in this pull request:

• Avoid React "inconsistent number of hook called" errors with two changes to the PanelStack2 implementation:
  • Move PanelStack2's early return in its render path to after all hooks are called
  • Wrap each renderPanel() call in a simple functional component wrapper to encapsulate the lifecycle of any hooks potentially called inside those functions
• Fix the PanelStack2 docs example state management to append and remove panels from the end of the stack array, rather than the beginning
  • The test suite and docs example were inconsistent about this. I believe the test suite had the correct behavior, and I've updated the docs to point this out for controlled mode users.

Reviewers should focus on:

• Any performance implications of the new <PanelWrapper />

Screenshot

[blueprint-bot]

address sebastian's PR comments

Previews: documentation | landing | table