Move default pip position to right above the shelf (Pt. Launcher)

SysUI change: ag/3721784, ag/3793664

- Track LauncherState and launcher activity state through callbacks.
- Devise logic to send shelf visibility and height signal to SysUI based
on LauncherState and Launcher activity state.

Bug: 73961893
Test:
- By default, pip shows up right above the shelf.
- Transitioning to all apps moves the pip down as the shelf becomes
invisible.
- Going to any specific app moves pip down. Hitting home moves pip
right above the shelf again.
- Dismissing IME should push PIP down but above the shelf on home
screen, bottom if not.

Change-Id: I1ab6ceb8007a5a7b5d932a456efa0a07f586ea4c