Use a fake task queue to test the RepeatingTask rather than a real
task queue, which removes the need for Sleep(). This fixes the flakiness
issues as the class is no deterministic.
BUG=webrtc:12808
Change-Id: I8c6a8535165b076f5fe6ec3e65ebcf7f07008737
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/237803
Reviewed-by: Tommi <tommi@webrtc.org>
Commit-Queue: Evan Shrubsole <eshr@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35349}
f0f474373c