[PiP2 on Desktop] Restore task to freeform bounds when exiting PiP.

Recall: http://recall/clips/ae803031-fcb0-46a3-b56f-0536d019daf3

Implement exiting/expanding PiP to freeform windowing mode if Desktop
Mode session is active on PiP2.

Bug: 378742351
Test: atest PipSchedulerTest
Flag: com.android.window.flags.enable_desktop_windowing_pip
Change-Id: Iba1b639012fa08824934783ec62f9092670237fd