Bug 991037 - Part 0: Stop sync waiting until GMP is ready, since this happens on main now and will deadlock. r=mt
Bug 991037 - Part 1: Simplify the command-queueing logic in pc.js, and make it less racy. r=mt
Bug 991037 - Part 2: Convert over to full trickle, which allows some simplification of code, and makes the following work much easier. r=mt
Bug 991037 - Part 3: Bring signaling_unittests up-to-date with the full-trickle behavior, and a fair bit of cleanup. r=mt
Bug 991037 - Part 4: Get rid of the sipcc threads/queues, and run all sipcc logic on main. r=mt