0.5

CHANGES:

features

• add Bb_queue.transfer

• add Bb_queue.to_{iter,gen,seq}

• add Fifo_pool, a simple pool with a single blocking queue for
  workloads with coarse granularity tasks that value
  latency (e.g. a web server)

• add a work-stealing pool for heavy compute workloads that
  feature a lot of await/fork-join, with a lot of help
  from Vesa Karvonen (@polytypic)

• add Fut.spawn_on_current_runner

• add Runner.{spawn_on_current_runner, await}

• add a few more toplevel aliases in Moonpool itself

• add No_runner: a runner that runs tasks synchronously in the caller

• on shutdown, pools will finish running all present tasks before
  closing. New tasks are immediately rejected.

• use an optional dependency on thread-local-storage to
  implement work stealing and spawn_on_current_runner

optimizations

• use the main domain to spawn threads on it. This means we can really
  use all cores, not all but one.
• in Fork_join.both, only one of the two sides schedules a task,
  the other runs in the current thread. This reduces scheduling overhead.
• compare to domainslib in benchmarks. With the WS pool we're now slightly
  ahead in terms of overhead on the recursive fib benchmark.

breaking

• deprecate Pool, now an alias to Fifo_pool
• the Fut.Infix_local and Fut.infix are gone, replaced with
  a simpler Fut.Infix module that tries to use the current runner
  for intermediate tasks.