Remote Connection Callbacks tests.

1. Adding CTS tests to test all the RemoteConnection callbacks.
2. Refactor all the existing RemoteConnection tests.
3. Added DTMF tests for RemoteConnection & RemoteConference.

BUG: 20303674

Change-Id: Ibe450a9868c8e4fe7a64c13706f5bd7c76b47877
2 files changed