Fix race when rotating the display during an entry into PIP

Rotating the display while the PIP task had just appeared caused
a race between the alpha entry animation starting and the rotation
controller handling that changes the PIP bounds, resulting in
a bounds mismatch between the surface that was animated and the
PipBoundsState.mBounds

This CL tracks whether we're still waiting for the alpha entry
animation to start when a rotation callback comes in, and
restarts the fade in after adjusting to the rotation.

Bug: 184664409
Test: In gesure nav, open YT go to fullscreen landscape mode and
launch another an activity from a notification - verify PIP fades
in and its bounds match the ones in PipBoundsState

Change-Id: I339d5088fb5f23f08fe8d548b9d02a34c16779d6