Removing functionality to choose congestion controller implementation, using injection instead. Also cleaning up some related functionality that's no longer needed, such as the injection of event logs into the factory. Bug: webrtc:9883 Change-Id: Ia528005625430ae31a15bc88881e2d4ac6ad1d42 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/133890 Commit-Queue: Sebastian Jansson <srte@webrtc.org> Reviewed-by: Björn Terelius <terelius@webrtc.org> Cr-Commit-Position: refs/heads/master@{#27768}