Also remove a bunch of functions in ChannelManager that were just forwarding to MediaEngineInterface. Bug: webrtc:13931 Change-Id: Ia38591fd22c665cace16d032f5c1e384e413cded Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/261304 Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org> Reviewed-by: Henrik Boström <hbos@webrtc.org> Commit-Queue: Harald Alvestrand <hta@webrtc.org> Cr-Commit-Position: refs/heads/main@{#36801}