Implement macros for PEP 518 & PEP 517 build systems

[mcepl]

See https://bugzilla.redhat.com/1685582 and there particularly links to https://discuss.python.org/t/pep-517-build-frontends-to-inform-users-about-wheel-basename/1026 and pypa/pip#6377

The first draft of proposed macros is

%pyproject_wheel: <flags...> %{__python3} -m pip wheel --no-deps --use-pep517 --no-build-isolation --progress-bar off --verbose .
+ conditional --global-option and --build-option based on %{?py_setup_args} and/or other macros.

%pyproject_install: %{__python3} -m pip install --root %{buildroot}  --strip-file-prefix %{buildroot} --no-deps  --progress-bar off *.whl

[sebix]

See also python-poetry/poetry#1338 (comment) poetry will drop setup.py soon and therefore all packages using poetry will not be installable with the standard way then.

[bnavigator]

The macros are in use and should be documented. #59

[mcepl]

I think the basic support of this has been included at least in 845439f.