Set up GHA to test on Python 3.9-beta and 3.8-dev

Fixed typo

Bugfix/tests for msvc spawn

In _msvccompiler.MSVCCompiler.spawn, use correct capitalization for PATH environment variable. Fixes failing test and fixes pypa/setuptools#2257.

In CCompiler, allow keyword arguments to be passed to spawn calls. Ref pypa/setuptools#2257 and pypa/distutils#5.

In TestSpawn.test_concurrent_safe, use CheckThread to ensure that the spawn call does not simply fail to execute. Ref pypa/setuptools#2257.

Suppress ImportError for winreg as the module is only available on some platforms. Allows unit testing of module on non-Windows platforms.

The PyPA has adopted the PSF code of conduct

For details, see:

* https://discuss.python.org/t/implementing-pep-609-pypa-governance/4745

Add docs on porting from distutils.

Remove logo

This reverts commit 0f491dc2.

This reverts commit 402880a7, reversing
changes made to bd110264.

This reverts commit fd94cd03.

This reverts commit 40564354.

Remove issue templates

The "setuptools warns about incompatibility" template has generated no
useful reports and should be removed.

Programmatically disable coverage when running on PyPy.

Warn the user when distutils is present

Warn the user when distutils is present to discourage this usage and direct users to the recommended usage. Closes #2230.

Test Python 3.9-dev on GitHub Actions

Fix race in spawn

Allow spawn to accept environment. Avoid monkey-patching global state.