resourcemanager: move utility functions

As part of refactoring the resource manager and the resources,
this change moves the utility functions out of the main
source code and into a new compilation unit.
Since, there is no change in the functionality or addition
or modifications of ResourceManagerService binder APIs,
this change is unflagged.

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
Merged-In: I49321e411e6671c547878ec947c553807829376a
Change-Id: I49321e411e6671c547878ec947c553807829376a