[1/?] Tests for generic BroadcastQueue.

Add test that verifies dispatching to multiple warm processes are
delivered and that the queue is flushed.  To keep the broadcast queue
flowing, the default mock ProcessRecord now immediately dispatches
finishReceiverLocked() back into the broadcast queue.

Bug: 243656033
Test: atest CtsContentTestCases:BroadcastReceiverTest
Test: atest FrameworksMockingServicesTests:BroadcastQueueTest
Change-Id: I6049b285f44cd891ce67faec76dfb1e1a92002cc