Removes all unused features, reducing the exposed interface surface. This makes refactoring and maintenance simpler as we can change TransportFeedbackAdapter without making corresponding changes to RtpVideoSender. Bug: webrtc:9883 Change-Id: If372a868e0765e94df52b4de52d3bb619ce11471 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/156943 Commit-Queue: Sebastian Jansson <srte@webrtc.org> Reviewed-by: Erik Språng <sprang@webrtc.org> Cr-Commit-Position: refs/heads/master@{#29649}