Fix ActivityEmbedding animation flicker

1. Fix flicker when rotate display with expanded TaskFragment:
   Only startChangeTransition if organizer request resizing, so we won't
   accidentally start the change transition for other resizing case,
   such as display rotation.
2. Fix flciker when exit split to fullscreen:
   Make sure to wait activity window redraw when the embedded
   TaskFragment is changing.

Fix: 258755905
Test: manual verify open fullscreen fixed-portrait embedded activity
      from landscape display.
Test: atest WmTests:WindowStateTests
Change-Id: Ifc825075abfb7c27461f23281f41425f66c3f680