Move code from P2PTransportChannel to Candidate, where we set the foundation value for remote prflx candidates. Bug: none Change-Id: I7dbcb85bca35dca7297136b0706092dd8d2b153c Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/339902 Reviewed-by: Philipp Hancke <phancke@microsoft.com> Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org> Reviewed-by: Harald Alvestrand <hta@webrtc.org> Cr-Commit-Position: refs/heads/main@{#41774}