merge_pr_56559

webrtc: unmute tracks until a packet arrives after a receptiveness change

This is gated by kMediaStreamTrackEmptyVideoFrameMonitor for more
deterministic behavior and kWebRtcUnmuteTracksWhenPacketArrives2
which is the new killswitch.

Bug: chromium:40821064
Change-Id: Ib0b87c8178d485565a9ead7883d673354617f858
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7216294
Commit-Queue: Philipp Hancke [email protected]
Reviewed-by: Henrik Boström [email protected]
Reviewed-by: Guido Urdaneta [email protected]
Cr-Commit-Position: refs/heads/main@{#1555346}