This CL first restricts Metrics to be retrievable when the socket is
created. This avoids having most fields as optional and makes it
easier to add more metrics.
Secondly, the peer implementation is moved into Metrics.
Bug: webrtc:13052
Change-Id: I6cb53eeef3f84ac34f3efc883853338f903cc758
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/262256
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36888}
f7fc71da44