disallowing more than one ssrc-group with the same semantic
and primary ssrc.
BUG=chromium:1477075
Change-Id: I4bce0555cd49834725d9b97693d26c971bc5d5c2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/318822
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Philipp Hancke <phancke@microsoft.com>
Reviewed-by: Sergey Silkin <ssilkin@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#40694}