Backport of "webrtc_sendrecv.py: Various fixes" into 1.22
Backport of !3742 (merged) "webrtc_sendrecv.py: Various fixes".
Commits:
- 6f99faa0 webrtc_sendrecv.py: Use sine wave for audio instead of red-noise
- 9b2404e7 webrtc_sendrecv.py: Add support for using H264 encoding
- 5500c228 webrtc_sendrecv.py: Add bus message handling
- 6a836026 webrtc_sendrecv.py: Handle LATENCY messages
- 32e8ff4e webrtc_sendrecv.py: Fix PEP8 warnings in CI lint