Move global state into a singleton class. Eliminates use of
GlobalMutex. Also use std::atomic rather than volatile, for improved
thread safety.
Bug: webrtc:11567
Change-Id: I305d16ed2f4a9a6497df119e66d9bba08337339a
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/258120
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36475}
00e93249ca