Simplifies PayloadRouter to not accept dynamically-changing modules as well as usage of PayloadRouter inside ViEChannel::SetSendCodec. BUG=webrtc:5494 R=stefan@webrtc.org TBR=mflodman@webrtc.org Review URL: https://codereview.webrtc.org/1725363003 . Cr-Commit-Position: refs/heads/master@{#11787}