Wiring up RTP Transport for D2D Communication.

- Adding configuration class in ImsPhoneCallTracker which is injected from
packages/services/Telephony to enable D2D comms.
- Set offered RTP header extensions when D2D comms enabled.
- Add some logging to track sending of D2D messages.

Test: Added unit test to verify ImsPhoneCallTracker sets the offered
RTP header extension types when D2D enabled.
Test: Added unit test to verify IPCT does not set offered RTP header
extensions whens D2D not enabled.
Test: Manual end to end test using adb shell command added for sending
D2D messages.
Bug: 163085177

Change-Id: I482cee19be369dc3d022c2fa57072f0cd63f87f8