Internal to Async -- a queue of jobs to run.

`module Scheduler = Async_kernel__.Scheduler0`
`type t``= Async_kernel__.Types.Job_queue.t```
`include sig ... end`
`val sexp_of_t : t ‑> Base.Sexp.t`
`include Core_kernel.Invariant.S with type t := t`
`type t`````
`val invariant : t Base__.Invariant_intf.inv`
`val create : unit ‑> t`
`val enqueue : t ‑> Async_kernel.Execution_context.t ‑> ('a ‑> unit) ‑> 'a ‑> unit`
`val clear : t ‑> unit`
`val set_jobs_left_this_cycle : t ‑> int ‑> unit`
`val can_run_a_job : t ‑> bool`
`val length : t ‑> int`
`val run_jobs : t ‑> Scheduler.t ‑> (unit, exn * Core_kernel.Backtrace.t) Core_kernel.Result.t`
`val num_jobs_run : t ‑> int`