This moves simple logic from SendSideCongestionController to
TransportFeedbackAdapter. The purpose is to make it easier to
reuse TransportFeedbackAdapter without requiring everything
in SendSideCongestionController.
Bug: webrtc:9586
Change-Id: I35acedd15001d75a06c38ece76868afecd6afa18
Reviewed-on: https://webrtc-review.googlesource.com/c/105106
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25177}