Clean away use of RtpAudioFeedback interface from RTP/RTCP receiver code. BUG=webrtc:4690 Committed: https://crrev.com/69a81999ace08e40e2b2ec526b0e111aa11b9538 Cr-Commit-Position: refs/heads/master@{#12015} Review URL: https://codereview.webrtc.org/1840893004 Cr-Commit-Position: refs/heads/master@{#12157}