MediaRouter2: Clean up APIs

Rename APIS related to RoutingController.
Specifically,
- requestCreateController is changed to transferTo, which is the only
way to "transfer" that may or may not create a controller.
- ControllerCallback is split into TransferCallback and
(new) ControllerCallback.
- onControllerCreated and onControllerReleased is merged into
onTransferred(old, new)

Rename APIS related to RoutingController.

Bug: 149185558
Test: atest android.media.cts.MediaRoute2InfoTest
  && atest android.media.cts.MediaRouter2Test
  && atest android.media.cts.RouteDiscoveryPreferenceTest
  && atest android.media.cts.RoutingSessionInfoTest
  && atest android.media.cts.MediaRoute2ProviderServiceTest
  && atest mediaroutertest

Change-Id: I348581be7c0b8537da22da3bc81e2ca31e16203f