Lazy-object-proxy

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* Added Python 3.12 wheels.
* Dropped support for Python 3.7.
* Applied some reformatting and lint fixes using ruff to the codebase (mostly more Python 2 leftover cleanups).

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* Added support for matrix multiplication operator (`).
* Should have all the wheels now (including the manylinux ones).
* Bumped minimum version requirements for setuptools and setuptools-scm.
* Switched the default pure python fallback implementation to the "simple" one (when you ``from lazy_object_proxy import Proxy``
and the C extension is not available).
Previously the "slots" implementation was used but as it turns out it is slower on Python 3.

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* Cleaned up use of cPickle. Contributed by Sandro Tosi in `62 <https://github.com/ionelmc/python-lazy-object-proxy/pull/62>`_.
* Cleaned up more dead Python 2 code.
* Added Python 3.11 wheels.
* Dropped support for Python 3.6.

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* Removed most of the Python 2 support code and fixed ``python_requires`` to require at least Python 3.6.

Note that 1.7.0 has been yanked because it could not install on Python 2.7.
Installing lazy-object-proxy on Python 2.7 should automatically fall back to the 1.6.0 release now.

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* Switched CI to GitHub Actions, this has a couple consequences:

* Support for Python 2.7 is dropped. You can still install it there but it's not tested anymore and
Python 2 specific handling will be removed at some point.
* Linux wheels are now provided in `musllinux` and `manylinux2014` variants.

* Fixed ``__index__`` to fallback to ``int`` if the wrapped object doesn't have an ``__index__`` method.
This prevents situations where code using a proxy would otherwise likely just call ``int`` had the object
not have an ``__index__`` method.

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* Added support for async special methods (``__aiter__``, ``__anext__``,
``__await__``, ``__aenter__``, ``__aexit__``).
These are used in the ``async for``, ``await` and ``async with`` statements.

Note that ``__await__`` returns a wrapper that tries to emulate the crazy
stuff going on in the ceval loop, so there will be a small performance overhead.
* Added the ``__resolved__`` property. You can use it to check if the factory has
been called.