To keep build-compatibility with Python 3.6, I've switched the build
backend from `setuptools` to `hatchling`. `setuptools` only supports
`pyproject.toml` from version 61 onwards, which itself isn't compatible
with Python 3.6. This does not mean we have to fully use Hatch as we can
still create build using `python -m build`. Hatchling automatically
includes all non-gitignored files, so the `MANIFEST.in` file has been
removed.

This adds an integration test that runs a set of mediawiki
containers, configures them enough that the API works, then runs
a few simple tests of logging in, creating, moving and deleting
pages. We also enable this in CI. We can extend this with more
tests later, I think this is a reasonable initial set.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

Signed-off-by: Adam Williamson <awilliam@redhat.com>

The latest incarnation of bumpversion is bump-my-version, which
considers .cfg configuration "deprecated" and wants it moved
to TOML, so here we go. We may as well move pytest config at
the same time as pytest has supported it for ages. We can drop
the "universal wheel" thing as that was about supporting Python
2 and 3 in the same wheel, and we don't support Python 2 any
more.

flake8 does not support pyproject.toml and it doesn't look like
you can specify aliases for setup.py there either, so we'll leave
those two in setup.cfg for now. Maybe in future we can get rid
of them.

Signed-off-by: Adam Williamson <awilliam@redhat.com>