Preparation CL to remove RTPTypeHeader. Follow up to this CL (https://webrtc-review.googlesource.com/c/src/+/83985). Bug: none Change-Id: I5da83f682bd72aec2f8d50998624de92e3404c58 Reviewed-on: https://webrtc-review.googlesource.com/84423 Reviewed-by: Stefan Holmer <stefan@webrtc.org> Commit-Queue: Philip Eliasson <philipel@webrtc.org> Cr-Commit-Position: refs/heads/master@{#23693}