Now that everything runs on their own loop and we don't cross the thread
boundaries (with few exceptions), most of the atomic_bool variables used
to track the socket state have been unatomicized because they are always
accessed from the matching thread.
The remaining few have been relaxed: a) the sock->active is now using
acquire/release memory ordering; b) the various global limits are now
using relaxed memory ordering - we don't really care about the
synchronization for those.
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