Implements a basic throttle. Users of the throttle must successfully call start_job
before beginning work and must call finish_job
once, and only once, when a job is
completed.
val create_exn : now:Time_ns.t ‑> max_concurrent_jobs:Core_kernel__.Import.int ‑> t
val finish_job : t ‑> now:Time_ns.t ‑> Core_kernel__.Import.unit