Mpservice

- Finetune to ``mpservice.multiprocessing.ServerProcess`` and its shared-memory facilities.
- Fix a bug in ``mpservice.mpserver.{Server, AsyncServer}`` related to input buffer.
- Finetune ``mpservice.mpserver.{Server, AsyncServer}`` internals.

- Breaking changes to ``mpservice.mpserver.Server`` API: the class is split into two classes: ``Server`` and ``AsyncServer``.
- ``mpservice.mpserver.Server.call`` got new parameter ``backpressure`` (previously only the async call has this parameter).
- Finetuned waiting and sleeping logic in ``mpservice.mpserver.{Server, AsyncServer}``; use ``Condition`` to replace sleeping.
- Made sure (or confirmed) that ``mpservice.mpserver.Server.call`` and ``mpservice.mpserver.Server.stream` are thread-safe.
- ``mpservice.streamer.Stream.peek`` finetune of printing; got new parameter ``prefix`` and ``suffix``.
- Refinements to classes ``mpservice.streamer.{IterQueue, IterProcessQueue, AsyncIterQueue}``.
- Refinements to ``mpservice.multiprocessing.ServerProcess``: further diverge from the standard class.
- Initial support for "shared memory" in the class ``mpservice.multiprocessing.ServerProcess``.

- New function ``mpservice.streamer.tee``.
- New class ``mpservice.streamer.IterProcessQueue``.
- Removed the "cancellation" "Event" mechanism in ``mpservice.mpserver.Server`` that was introduced in 0.12.7.
There are two main reasons for the removal: (1) the ``mpservice.multiprocessing.manager.Event`` that is checked
by every worker seems to have considerable overhead although I did not measure it; (2) there is
difficulty in maintaining a reference to the ``Event`` object in the event of cancellation to
ensure any worker that tries to access it will do so before it is gone in the manager process;
this issue manifests as ``KeyError`` during unpickling when the object is being retrieved from
a multiprocessing queue.

- Removed ``mpservice.mpserver.{ProcessWorker, ThreadWorker}``; just use ``Worker``.
- Renamed ``mpservice.mpserver.make_threadworker`` to ``mpservice.mpserver.make_worker``.
- ``mpservice.mpserver.Server`` got new method ``async_stream``.
- New classes ``mpservice.streamer.IterQueue``, ``mpservice.streamer.AsyncIterQueue``.
- Minor tuning of ``mpservice.multiprocessing.ServerProcess``.

Removed

- Methods ``mpservice.streamer.Stream.{async_parmap, parmap_async}`` are dropped and merged into ``parmap``.
- Function ``mpservice.http.run_app``.

Changed

- ``mpservice.streamer.Stream.parmap``: parameter ``executor`` became named only.
- ``mpservice.multiprocessing.Manager`` was renamed ``ServerProcess``.
- Parameter ``backlog`` to ``mpservice.mpserver.Server.__init__`` was renamed to ``capacity``.

Added

- ``mpservice.streamer.Stream`` added extensive support for async.
- Methods ``mpservice.streamer.Stream.{to_sync, to_async, __aiter__}``.
- Method ``mpservice.mpserver.Server.full`` and properties ``mpservice.mpserver.Server.{capacity, backlog}``.
- Added capabilities to cancel a item submitted to ``mpservice.mpserver.Server`` and halt its processing in the pipeline as soon as practical.
- Made ``mpservice.mpservice.multiprocessing`` more close to the standard ``multiprocessing`` in terms of what can be imported from it.
- New parameter ``name`` to ``SpawnContext.Manager``.
- ``SpawnProcess`` captures warnings to logging.

Added

- New method ``mpservice.streamer.Stream.async_parmap`` with corresponding class ``AsyncParmapper``.

Improved

- The cleanup or "finalize" logic of ``mpservice.streamer.{Buffer, Parmapper, AsyncParmapper, ParmapperAsync}``.