Converge transition GC logic for userfaultfd GC with AOSP

Due to an incorrect conflict resolution while cherry picking
947b322d2c38dea414e9578d25dcf6f1d3963102 to this branch, the logic of GC
triggering while transitioning app (foreground/background) diverged for
userfaultfd GC as compared to CC.

Bug: 282230491
Bug: 160737021
Test: manual
Change-Id: I992d9d345b6a2f880e406fa94586d13c086013fb
Merged-in: I6d4a3f1285dcb1556cbf6a913b9ae43d840c84e2