Changed the cached threshold that decides when to defer bcasts.

Currently, we use RECEIVER procstate (indirectly through
onUidCachedChanged callback) as threshold for deciding when to
defer broadcasts. Change it to LAST_ACTIVITY procstate which is
closer to the "freezable" state we would like to use.

Bug: 275142200
Test: atest ./services/tests/mockingservicestests/src/com/android/server/am/BroadcastQueueModernImplTest.java
Test: atest ./services/tests/mockingservicestests/src/com/android/server/am/BroadcastQueueTest.java
Change-Id: I58c5c2cc44e391f64771d2331d7f86b27e6d60f7