Add ThirdPartyCall APIs to master

These are APIs for the new ThirdPartyPhone feature.

Note, these APIs can't actually be used yet on master for two reasons:
  - initiating a call from a 3rd party app isn't possible yet because
    the TelephonyManager APIs aren't being added to master.
  - the TeleService implementation of these APIs aren't being added to
    master.

Also, these APIs will be removed and the final ones will be added
once they're ready to be merged into master.

Change-Id: Ie783290451da448a011f813983e55b12047b5d99