MNT: migrate away from distutils

[neutrinoceros]

The distutils builtin package is slanted for removal in Python 3.12, which should be released around October 2023.
It is currently used in several places in yt, making it de facto incompatible with Python 3.12

In #3380, among other things, I'm setting an explicit upper limit to compatible Python versions, as a temporary bandaid that can be shipped with yt 4.0, but it'd be preferable to solve this for 4.1, at the latest.

Note that we are already specifying setuptools (not distutils) as our build system in pyproject.toml, which means that migrating away from the bits of distutils that we do use (most importantly in setupext.py) should be trivial.

I do not know how hard (or necessary) it would be to migrate away from distutils directives (first introduced in #2509).

useful resources:
https://setuptools.pypa.io/en/latest/deprecated/distutils-legacy.html?highlight=distutils
https://www.python.org/dev/peps/pep-0632/#migration-advice

Originally posted by @neutrinoceros in #3380 (comment)

[neutrinoceros]

upstream issues worth keeping an eye on

• how to handle numpy.distutils and setuptools interaction pypa/setuptools#2372
• Expose compiler classes for customized use pypa/setuptools#2806

[neutrinoceros]

I'm taking action upstream to cut the remaining ties we have to distutils, see pypa/setuptools#3445

[neutrinoceros]

Discussions with setuptools maintainers helped clarified that we can still rely on setuptools' compatibility shim for distutils for now.
pypa/setuptools#2806 (comment)

This means that yt will still build on Python 3.12 as long as the shim is maintained, but it will also be removed at some point. An implication is that we should start pinning setuptools on release branches to make sure that releases can still be built from source in the future.
I've renamed this issue to better convey the actual problem.