This helper class currently lives in `modules/video_coding`,
but it's only users are in `video/`. Thus, it makes sense to
move the class to `video/`.
Bug: webrtc:14116
Change-Id: I0d3f8961bc8f5fe80f3100dbbd309b206020e6d5
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/262963
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Commit-Queue: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36973}
