Revise homepage highlight mechanism

- Create TopLevelHighlightMixin to handle highlight actions and simplify
  TopLevelSettings
- Fix the error highlight and the flicker after screen rotation
- Postpone creating the fragment until it's needed to accelerate the
  initialization and to fix the search highlight function breakage after
  toggling light/dark mode
- Register activity embedding rules only once for injection and
  wallpaper
- Do not highlight Tips & support since it's full screen
- Refactor ActivityEmbeddingRulesController

Bug: 207316936
Test: manual, robotest build pass
Change-Id: If322ec180b03ee123987c70779a25c6a570d9faf