Mpservice

- Further finetune of importing paths of things, esp in ``mpservice.multiprocessing``.
- Some improvements to documentation.

- Adjustment to the importing of things in ``mpservice.multiprocessing``. Some changes are breaking.
``mpservice.multiprocessing.context`` has become ``mpservice.multiprocessing._context``.
``mpservice.multiprocessing.util`` has been removed.

- New http serving code in ``mpservice.http`` designed for multiple worker processes
managed by ``uvicorn`` (as opposed to multiple worker processes managed by ``mpservice.mpserver``).
- Removed dependency on ``asgiref``.
- ``Stream.groupby`` now behaves like the standard ``itertools.groupby`` in that the subgroups it yields are generators rather than lists.
- ``Stream.{map, filter}`` now can take async ``func`` arguments.
- New method ``Stream.shuffle``.

- Bug fix.
- Remove previously deprecated code.

- Deprecated ``mpservice.multiprocessing.util.CpuAffinity``.
- Refinement to ``get_shared_thread_pool`` and ``get_shared_process_pool``.
- Removed the constant ``MAX_THREADS`` from ``mpservice.threading``.

- Removed "IterableQueue" and variants, as well as ``StreamServer``, from ``mpservice.experimental``.
- Revised ``mpservice.experimental.streamer.EagerBatcher`` to not use ``IterableQueue``. This makes it simpler and more usable.