[PIP2] Add Shell requested remove PiP transition.

Recall: http://recall/clips/91a0fe99-d96b-4639-9812-03167a33c4b0

Bug: 372048924
Bug: 372320038
Test: Launch PiP and manually verify remove button on PiP menu removes
PiP window.
Flag: com.android.wm.shell.enable_pip2

Change-Id: Icad8428a6e28eb1d27d0220976e9acd93a32327d