Implement auto-enter PiP2 in gesture nav [4/N]

When auto-entering PiP through gesture navigation
directly start a TRANSIT_PIP transition in
RecentsController#finishInner().

Merge the finishWCT meant for finishTransition()
into TRANSIT_PIP's startWCT instead to make sure
all the visibility updates are made after moving
the activity to a pinned root task as a hierarchy-op.

This would also make sure that setConfigAtEnd() properly
pauses the PiP activity's config updates since at first
after startTransition() its state would be RESUMED and
isVisibilityRequested=true.
moveActivityToPinnedRootTask() makes sure the state becomes
PAUSING (if not done by startPausing already in Recents transition).
This is followed by an already present call to schedulePauseActivity().

Eventually, the activity remains in PAUSED state
as enforced by the CTS tests.

Bug: 325481148
Test: manually swipe up auto-enter PiP
Change-Id: I58d330e816101da7bcf328b9dccf092f2bdd99cb