Factor fixed rotation in app compat PiP expand

AppCompatTaskInfo's letterbox bounds are based on an
activity's resolved configuration. This means when
in fixed rotation, since the topActivity is in a different
orientation, the letterbox bounds will be in that final orientation.

On the other hand, in fixed rotation transitions, there is no actual
display rotation happening yet - that would be in the follow-up async
rotation. Hence, all the bounds of resolved targets are in the display
rotation still.

Therefore, when fixed rotation PiP exit-via-expand animation is about to
run, we have to "rotate" the letterbox bounds to current display
rotation, before it's factored into the endBounds.

As a follow up, handleExpandFixedRotation() will modify those endBounds,
and both rotate and shift them around origin to prepare for expand
animation.

Bug: 435131413
Flag: EXEMPT bugfix
Test: expand from PiP with fixed rotation in ApiDemos or any other app
  compat PiP activity
Change-Id: Iaab741d38d668eba148fb3a550fdb4342a0ac1e7