To allow objc video encoders to support scalability modes Bug: b/299588022 Change-Id: Id58f996b8c48c6688cccdc32caff6adb00370d5c Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/358580 Reviewed-by: Kári Helgason <kthelgason@webrtc.org> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/main@{#42985}