Promote app transition target its ancestor if possible.

Previously we only animated ActivityRecord. When hierarchical animation
is enabled, we find the top most entity from the window hierarchy (i.e.
ActivityRecord < Task < ActivityStack) which we can animate without
user visible changes, and set app transition animation on it.

The hierarchical animation is disabled by default. To enable it,
system property "persist.wm.hierarchical_animations" must be set.

Test: atest AppTransitionControllerTest
Bug: 131661052
Change-Id: I4709fd178de09d289d72cf1833b056b4e34fc92b