This converts all P2PTransportChannel unit tests to parameterized tests, with a string parameter for the field_trials which is used to enable the refactor. This adds a variation of each existing test using the refactored code path. Tests are initialized twice, once for legacy and refactored path each, to strike a balance between file name length and descriptiveness. Bug: webrtc:14367, webrtc:14131 Change-Id: I0469550d571ed389804eb486fe5bd22504e59373 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/275303 Commit-Queue: Sameer Vijaykar <samvi@google.com> Reviewed-by: Jonas Oreland <jonaso@webrtc.org> Cr-Commit-Position: refs/heads/main@{#38162}