mypy_mypyc-wheels: rewrite using Github Actions and cibuildwheel

[hauntsaninja]

There are more details over at python/mypy#9536
These changes go together with python/mypy#9570

[hauntsaninja]

List of improvements we can make once this is merged:

• Once my MANIFEST.in change is merged, see if we can remove the copying over of pytest files hack (which I inherited from https://github.com/python/mypy/blob/master/misc/test_installed_version.sh)
• That will also allow us to run check-manifest as a step here
• Add mypyc requirements to pyproject.toml so isolated builds are possible
• Run some tests against sdist and Python wheel
• Factor some of the repetition in this file

[msullivan]

This seems pretty reasonable to me and we should move forward with it. We should coordinate merging it so I can bother you about any "fine-tuning" that needs to be done.

[hauntsaninja]

Thanks, sounds good! I'll be around any weekend in the next month to fix issues that may arise.
Might be wise to wait until we're sure we don't need to make any more 0.79* releases (e.g., do we need a new release for python/mypy#9584?)

[mr-c]

@hauntsaninja a 0.791 release to fix building mypyc from the sdist would be appreciated for Debian and other packaging systems

[hauntsaninja]

I don't have the ability to make that happen, but I posted on your behalf at python/mypy#9290 :-)

[mr-c]

@hauntsaninja thanks! Debian patched around the issue (and cherry picked the Python 3.9 patches) but I'm sure other distributions and packaging systems would appreciate it.

[JukkaL]

I'm going to make the 0.791 release soon.

[hauntsaninja]

@msullivan Shall we go ahead and merge? I'll be able to fix any issues that come up this weekend / it might make sense to give me write access to this repo

(Also not fully sure what needs to be done to tell AppVeyor it's over between us)

[JukkaL]

@hauntsaninja I gave you access to this repository. Please let me know if there something else that you need to allow you to move this PR forward. This will be great to have, and I now have more time to help with this.