Convert the abstract GoogleCameraHelper class to an interface

* The legacy class cannot be removed since the older prebuilts cannot be
regenerated. Going forwards, we will ensure that the automation for live
and tested versions are retained in case an update like this happens
again.
* This strategy works because the abstract class now inherits from the
interface. Anyone searches for the interface will also return
older implementations for the abstract class, maintaining backwards
compatibility.
* Deprecates the AbstractGoogleCameraHelper.

Bug: 36491973
Test: manual
Change-Id: I4ae848de1aaef2e60ef779895a650c20cdd6d4df