* Make StunRequest::manager_ a reference, inject ref at ctor time.
* Make other member variables private.
* Mark methods that are only used for testing with "ForTest"
* Add RTC_GUARDED_BY for member variables and thread checks.
* Remove/reduce 'friend'-ness between classes.
* Use std::unique_ptr for owned and passed message pointers.
* Rename `requests_` to `request_manager_` (type: StunRequestManager)
Bug: webrtc:13892
Change-Id: I3a5d511b3c2645bb6813352d39e9fefe422dd1de
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/258620
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36529}
86aa03e238