cancellation: Hook up libuv to cancellation (#62557)
Part of the larger #60281 work.
Extends the wait protocol from #62430 with support for multiple simultaneous wait queues.
This is then used for the various libuv call sites to wait for both libuv and cancellation simultaneously.
The bulk of the rest of the work is just threading this through to every corner of the IO system.
Co-authored-by: Keno Fischer <Keno@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
