Skip predict back animation to translucent activity.

The cross-activity animation can be weird if previous activity is
translucent, also skip animation for those case.

Refine canShowWhenLocked condition since previous activity can be
multiple

Bug: 307459377
Test: manual, trigger back to a translucent activity.
Test: atest BackNavigationControllerTests
Change-Id: I69fb56e8347ca2bd3237695e6ee6d3ecc84f0fd9