This CL adds `Y4mFrameGenerator` to support Y4M file input. Bug: webrtc:15210 Change-Id: If21e40a609b3c6f980a413fb183cd4dfb5123aab Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/311520 Commit-Queue: Jianhui J Dai <jianhui.j.dai@intel.com> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Cr-Commit-Position: refs/heads/main@{#40460}