Python packaging after distutils: `setuptools.build_meta` ?

[alexsavulescu]

After #2076 wrt PE632, we may consider using the setuptools.build_meta build system as opposed to setuptools (which technically holds its own distutils implementation).

Notes:

• based on the PEP 517 specification. Compared to traditional "setuptools" build process that relies on the "setup.py" script, the build process is defined in a separate configuration file called "pyproject.toml", which in principle allows for greater flexibility and customization in the build process (?).
• we should use the "pyproject.toml" configuration file to specify build and metadata information, and avoid using "setup.py" altogether. However it stands to reason our complex setup.py (CMake, cython, ...) may require substantial work for this.
• it is possible to still rely on setup.py (see #2226), but this legacy mode is slated for removal since it is considered temporary. This approach may be required depending on future evolution of setuptools

[JCGoran]

Other viable build backends are:

• scikit-build (currently used by NMODL)
• scikit-build-core (complete rewrite of scikit-build, fully supports pyproject.toml, has support for static cmake options, but some features still experimental)