Allow setting a connection callback to PersistentServiceManager.

Add methods to PersistentServiceManager to add/remove a connection
callback. This is needed to fix an issue with the cast icon not
appearing correctly when docked and dreaming.

Also add dumpsys logging to PersistentServiceManager and
ObservableServiceConnection to aid debugging connection issues.

Bug: 314690485
Test: atest PersistentServiceManagerTest,
ObservableServiceConnectionTest
Flag: NA

Change-Id: I75fc633d0ccb88cb45ace201190c51f67ba42248