Refactoring of auto fill - lifecycle, auth, improvements

1. Move management of the remote fill service in a dedicated
   class that abstracts away the async and ephemeral nature
   of the binding.

2. Update auth to move fingerprint out of the platform and
   allow response and dataset auth.

3. Cleaned up the fill and save callback classes.

4. The UI is now shared among all sessions and cleaned up.

5. Reshuffled the remote callbacks to have cleaner separation.

6. Cleaned up and tightened the reponse and dataset classes.

7. Added API to support communicationn with intent based auth.

Test: CTS + manually

bug:31001899

Change-Id: Idc924a01d1aea82807e0397ff7293d2b8470d4d6