Merges SetRecvCodec/SetRecvExtensions and an extra call for changing RTCP mode, resulting in recreating the stream at most once instead of up to three times. BUG=webrtc:5296 R=deadbeef@webrtc.org, pthatcher@webrtc.org Review URL: https://codereview.webrtc.org/1641863004 Cr-Commit-Position: refs/heads/master@{#11422}