Test and build using PEP 517-compliant methods

[movermeyer]

We shouldn't be using python setup.py sdist nor python setup.py test anymore:

$ python setup.py test
running test
WARNING: Testing via this command is deprecated and will be removed in a future version. Users looking for a generic test entry point independent of test runner are encouraged to use tox.
/home/mike/.pyenv/versions/3.12.0/lib/python3.12/site-packages/setuptools/command/test.py:193: _DeprecatedInstaller: setuptools.installer and fetch_build_eggs are deprecated.
!!

        ********************************************************************************
        Requirements should be satisfied by a PEP 517 installer.
        If you are using pip, you can try `pip install --use-pep517`.
        ********************************************************************************

!!
  ir_d = dist.fetch_build_eggs(dist.install_requires)
WARNING: The wheel package is not available.

We should be moving as much as possible into pyproject.toml.

However, this may prove tricky to do while supporting old versions of Python.

For example: At present, tox only supports Python 3.7+

So there will be discussions of how much we're willing to lose/change to stay in line with modern Python testing/packaging methods.