Eio_utils.ZzzA set of timers.
module Key : sig ... endA handle to a registered timer.
val create : unit -> tcreate () is a fresh empty queue.
add t time item adds a new event, due at time, and returns its ID.
If item is a Fiber, you must use Eio.Private.Fiber_context.set_cancel_fn on it before calling pop. Your cancel function should call remove (in addition to resuming it).