This cl introduce RegisterReceivedPacketCallback and
DeregisterReceivedPacketCallback that will be used to replace AsyncPacketSocket::SignalReadPacket
A "proof of concept" cl is here: https://webrtc-review.googlesource.com/c/src/+/327324
Bug: webrtc:15368
Change-Id: I07e4f564dc8420d78e542991689778d8531225df
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/327325
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Per Kjellander <perkj@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#41164}
