Consider adding a pyproject.toml for PEP 517

[ca-hu]

The libselinux python bindings and the sepolicy python module use setup.py without a pyprojects.toml.

./libselinux/src/setup.py
./python/sepolicy/setup.py

Which leads to deprecation warnings, e.g.:

[   22s] python3.11 -m pip install --prefix=/usr `test -n "/home/abuild/rpmbuild/BUILD/policycoreutils-3.10-build/BUILDROOT" && echo --root /home/abuild/rpmbuild/BUILD/policycoreutils-3.10-build/BUILDROOT --ignore-installed --no-deps`  .
[   23s] WARNING: Disabling truststore because of missing certificates
[   23s] Processing /home/abuild/rpmbuild/BUILD/policycoreutils-3.10-build/policycoreutils-3.10/sepolicy
[   23s]   Preparing metadata (setup.py): started
[   23s]   Preparing metadata (setup.py): finished with status 'done'
[   23s] Building wheels for collected packages: sepolicy
[   23s]   DEPRECATION: Building 'sepolicy' using the legacy setup.py bdist_wheel mechanism, which will be removed in a future version. pip 25.3 will enforce this behaviour change. A possible replacement is to use the standardized build interface by setting the `--use-pep517` option, (possibly combined with `--no-build-isolation`), or adding a `pyproject.toml` file to the source tree of 'sepolicy'. Discussion can be found at https://github.com/pypa/pip/issues/6334
[   23s]   Building wheel for sepolicy (setup.py): started
[   23s]   Building wheel for sepolicy (setup.py): finished with status 'done'

More information can be found here: pypa/pip#6334

ATM it is still mostly backwards compatible, but we have run into issues with build isolation lately:
https://bugzilla.suse.com/show_bug.cgi?id=1258173