Add support for DTMF and RTP header extension communications.

Add support for:
- reporting of incoming DTMF tones from IMS stack.
- incoming/outgoing RTP header extension data.

Test: Added unit tests where possible.
Test: Added test intents to inject test data into framework for platform
testing.
Bug: 163085177
Change-Id: If34faeba0461c677a1381c82ead4a79c607bcf13