Fix the scrolling behavior in Settings homepage

- we always scroll to top of homepage first.
- if target position already exist on screen,
  we don't need to scroll.
- if target position doesn't exist on screen,
  scroll to the target position.

Bug: 349696107
Test: manual
Flag: com.android.settings.flags.homepage_revamp
Change-Id: I18c314d19eb38f22f799cb8bf087bf71f4f7d466