[PB] Migrate visibility change to transition.

There are two possible visibility change during predictive back
animation.

1. No snapshot for previous activity.
Currently core use setLauncherBehind to make previous activity become
visible. To migrate the visibility change in transition, create a
TRANSIT_PREPARE_BACK_NAVIGATION transition in core, and handle that
transition in BackTransitionHandler once it received handleRequest.

2. Close transition after gesture release.
For close home/task/activity case, core should expect a close
transition happen. The BackTransitionHandler can distingush that close
transiton by FLAG_BACK_GESTURE_ANIMATED.

If another transition happen while first transition is playing, just
finish first transition and cancel the predictive back animation, so
the next transition can play by corresponding handler.

In both 1 & 2 case, apply start transaction to remove windowless surface,
and reparent to the exist animation leash if needed. For no transition
cases(i.e. close window) the finish signal still passing by animation
finish callback.

Bug: 347168362
Flag: com.android.window.flags.migrate_predictive_back_transition
Test: atest BackNavigationControllerTests BackAnimationControllerTest
Test: verify back-to-home/cross-activity/cross-task transition can be
closed smoothly after back gesture trigger.

Change-Id: Ic70e16c57b4aca0d4d4275f788985027324b4e4c