Add simulated time support to CallTest

Allow CallTest subclasses to run under simulated time by providing
constructors that accept a TimeController pointer or unique_ptr ownership.
When a TimeController is configured, CallTest passes it to
CreateTestEnvironment and creates network and transport threads via
TimeController::CreateThread instead of using physical threads.

In RtpRtcpObserver, add Wait(TimeController*) to allow waiting under
simulated time without blocking real-time execution.

Migrate CodecEndToEndTest and EndToEndTestH264 to run with
GlobalSimulatedTimeController, resolving long runtimes and timeouts on trybots.

Bug: None
Change-Id: Ia33271bdf6262fd85461c9284048cd3b6bc00c3b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/500822
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48531}