This is part of the following reland cl:
https://webrtc-review.googlesource.com/c/src/+/105600
Adding just the new location of MockVideoEncoder first and updating
downstream projects before relanding the rest of that change.
Bug: webrtc:9722
Change-Id: I44ba65a72cde1eea62ee4520d8e84472f4e41c0f
Reviewed-on: https://webrtc-review.googlesource.com/c/105620
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25144}