Fix deadlock in binder death handling

CallbackRecord.binderDied() triggers a new thread that tries to lock
CallbackRecord.mCallbacks.  Thus, binderDied() may not be called while
holding mCallbacks.

This change moves the exception handler for RemoteException
(indicating that the remote end has died) out of synchronization
blocks on mCallbacks.

Flag: com.android.server.am.defer_display_events_when_frozen
Bug: 388848221
Test: atest
 * DisplayServiceTests
 * CtsDisplayTestCases
Change-Id: Ib4a62ccc99725eb0c8f97ff2934fd19fc22417d3