Mpservice

- Finetune exit status handling of ``SpawnProcess``.
- ``mpservice.mpserver.StreamServer`` was moved into ``mpservice.experimental.mpserver``.
- Parameter ``main_cpu`` to a few functions in ``mpservice.mpserver`` was removed.
- Default value of parameter ``timeout`` to ``mpservice.mpserver.Server.stream`` and ``mpservice.mpserver.AsyncServer.stream``
were changed from 600 to 3600, so that user almost never need to specify this parameter.
- in ``mpservice.mpserver``, if a Worker fails to start, the exception will propagate through ``Servlet.start`` into ``Server.__enter__``.

- ``mpservice.mpserver.{ProcessServlet, ThreadServlet}`` get new parameter ``worker_name``.
- Added trivial subclasses of the standard ``queue.{Queue, SimpleQueue}``, ``asyncio.Queue``, ``multiprocessing.queues.{Queue, SimpleQueue}``; the subclasses are generic, hence can take annotations for the type of the elements contained in the queues.
- New subpackage `mpservice.experimental`; moved all the few types of ``IterableQueue`` as well as ``mpservice.streamer.EagerBatcher`` into it.
- Import some subpackages in ``__init__.py``.

- New class ``mpservice.streamer.EagerBatcher``.
- New class ``mpservice.mpserver.StreamServer``. This intends to eventually replace and deprecate ``mpservice.mpserver.Server.stream``,
but the current version has not shown speed benefits yet, despite being simpler.
- Speed improvements to ``mpserver`` and ``streamer``.
- ``mpservice._streamer.{IterableQueue, IterableProcessQueue, AsyncIterableQueue}`` were moved into
``mpservice.queue``, ``mpservice.multiprocessing.queues``, ``mpservice.asyncio`` respectively and all renamed to ``IterableQueue``.
- A few utility classes in ``mpservice._streamer`` are now exposed in ``mpservice.streamer``, including ``Batcher``, ``Unbatcher``, ``Buffer``.

- ``IterableQueue``, ``IterableProcessQueue``, ``AsyncIterableQueue`` became generic with an element type parameter.
- Parameter ``cpus`` to ``ProcessServlet.__init__`` now accepts an int, indicating number of unpinned processes.
- Use more reliable way to infer whether a ``Stream`` object is sync or async iterable.
- Fixed issues in documentation generation.

- New methods ``mpservice.threading.Thread.{raise_exc, terminate}``.
- New functions ``mpservice.threading.{wait, as_completed}``.
- Enhancements to ``mpservice.multiprocessing.server_process`` esp regarding "hosted" data.
- Do not raise exception if a ``mpservice.multiprocessing.context.SpawnProcess`` was terminated by ``.terminate()``.
The previous behavior tends to raise exception when a ``ServerProcess`` shuts down.
- ``mpservice.mpserver.Worker`` adds support for ``preprocess``.
- Revised implementation of ``mpservice.multiprocessing.context.SpawnProcess`` to use a Future to support ``wait`` and ``as_completed``.
- New functions ``mpservice.multiprocessing.{wait, as_completed}``.
- Renamed ``mpservice._streamer.{IterQueue, IterProcessQueue, AsyncIterQueue}`` to ``{IterableQueue, IterableProcessQueue, AsyncIterableQueue}``.
- Finetune implementation of ``mpservice._stramer.{IterableQueue, IterableProcessQueue, AsyncIterableQueue}``.
- Made ``mpservice._streamer.Stream`` generic to allow type-annotating ``Stream[T]``.

- Re-orged ``mpservice.multiprocessing`` into a sub-package as the module has grown considerably and may grow further.
- ``mpservice.mpserver.{Server, AsyncServer}`` bug related to "gather-output" and "notify" requesters.
- Enhancements to ``mpservice.mpserver.multiprocessing.ServerProcess`` (in progress).