resourcemanager: rework death handling

remove the dependency on static lock and maps
for handling death notifications.

Bug: 289097671
Test: atest android.media.misc.cts.ResourceManagerTest
      atest android.media.misc.cts.ResourceManagerMultiTest
      /data/nativetest64/ResourceManagerService_test/ResourceManagerService_test
      /data/nativetest64/ResourceObserverService_test/ResourceObserverService_test
Change-Id: Iaed7d5141458e31803ffdefa5fee67497d33d7c1