Camera multi-client priority changes update

When multiple clients have opened the camera in shared mode, and the
priority of any client changes in the middle of session then notify
the clients of any shared client priority changes from either primary
to secondary or vice versa.

Flag: com.android.internal.camera.flags.camera_multi_client
Bug: 392781619
Test: run CTS test SharedCameraTest#testClientSharedAccessPriorityChanged
Change-Id: I50111a5338521c2e25bbf049e97b707f01ce6773