[PB] Filter out activity transition under TaskFragment

...from predictive back transition.
1. The opening target in predict_back transition could be multiple
   because of activity embedded adjacent.
2. To be more accurate to filter out none participant predictive back
   transition targets, checking the opening type, and prevent the
   predictive target involved into app transition.

Flag: EXEMPT bugfix
Bug: 375111994
Test: atest BackAnimationControllerTest
Test: Back to activity adjacent, and verify the transition when both
commit and cancel gesture can work as expect.
Test: tap on the edge of Settings multiple times, verify the activity
embedded changes can be filter out from back transition handler, and
corresponding handler can play with the transition.

Change-Id: I1f527770eaa8b542215a6d679c86f9873f659993