Store "cached" state separate from ProcessRecord.

It ends up that ProcessRecord.isCached() isn't maintained with the
same lifecycle as onUidCachedChanged(), so we pivot to maintaining
our own collection of last-reported cached states.

Bug: 276243219, 275142200, 275594411
Test: atest FrameworksMockingServicesTests:BroadcastQueueTest
Test: atest FrameworksMockingServicesTests:BroadcastQueueModernImplTest
Test: atest FrameworksMockingServicesTests:BroadcastRecordTest
Change-Id: I83531444df5c467a54da9c7fa53eea206677b6e1