Replicates bounds calculation to SysUI package

This new PipBoundsHandler class handles bounds calculation for PiP on
Phone and other form factors, it keeps tracking variant state changes
originated from Window Manager and is the source of truth for PiP window
bounds.

What's next
- Wire the state changes from WM to PipBoundsHandler
- Switch to PipBoundsHandler for bounds calculation on entering PiP
- Deprecate the bounds calculation in PinnedStackController

Bug: 139015142
Test: N/A
Change-Id: I305fe8daa8a2b6eaf955843aea121226f99f8e1e