sceRudpPollCancel waited until no wait was registered, so a wait that
started during the drain kept it blocked, forever for an infinite one.
Waits registered when the cancel starts now move to a draining count,
and the cancel returns once those have left. A scope guard releases each
wait's registration on every exit, retaking the lock if the wait had
dropped it, so an exception in the condition wait no longer leaves a
registration that a later cancel can never drain. Reported by
@MarcZX10, @thepoppfish, @adriadam10 and @oneandonlydean; the guard
follows @thepoppfish's repair.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
