Add WCT to disable Task to enter PiP

PiP and Bubble provide a similar UX for putting a Task on the side, so
we want to disable PiP if the Task is already in Bubble.

Bug: 389158353
Flag: com.android.window.flags.disallow_bubble_to_enter_pip
Test: atest WmTests:WindowContainerTransactionTests
Test: atest WmTests:ActivityTaskManagerServiceTests
Change-Id: I386a31512ab00a4562ba2a9703273ee0968bbe77