Add multi-desk support for tiling.

This cl adds multi desk support for tiling, by swapping the displayId key
within the tilingViewModel with the deskId concept.

the CL also tracks desks that are being hidden and hides the divider, and
tracks when a task is removed from a desk to remove it from the tiling
session.

Flag: com.android.window.flags.enable_tile_resizing
Flag: com.android.window.flags.enable_multiple_desktops_backend
Test: unit tests and on device testing
Bug: 411433308
Change-Id: I15dd185a5c43ba226d6022a76bf058a2b8f17e8c