Replace UserHandle hidden API references

This is a Telecom Mainline cleanup CL that removes the dependencies on hidden UserHandle APIs and replace them with the public API Binder#getCallingUserHandle.

Test: atest DefaultDialerCacheTest
Flag: com.android.server.telecom.flags.resolve_hidden_dependencies_two
Bug: 308209390
Change-Id: I6c123a92b52edf99236d5fadc567caad7162c1ce