python: add qapi static analysis tests

python: add qapi static analysis tests

Update the python tests to also check QAPI and the QAPI Sphinx
extensions. The docs/sphinx/qapidoc_legacy.py file is not included in
these checks, as it is destined for removal soon. mypy is also not
called on the QAPI Sphinx extensions, owing to difficulties supporting
Sphinx 3.x - 8.x while maintaining static type checking support. mypy
*is* called on all of the QAPI tools themselves, though.

flake8, isort and mypy use the tool configuration from the existing
python directory (in setup.cfg). pylint continues to use the special
configuration located in scripts/qapi/ - that configuration is more
permissive. If we wish to unify the two configurations, that's a
separate series and a discussion for a later date.

The list of pylint ignores is also updated, owing again to the wide
window of pylint version support: newer versions require pragmas to
occasionally silence the "too many positional arguments" warning, but
older versions do not have such a warning category and will instead yelp
about an unrecognized option. Silence that warning, too.

As a result of this patch, one would be able to run any of the following
tests locally from the qemu.git/python directory and have it cover the
QAPI tooling as well. All of the following options run the python tests,
static analysis tests, and linter checks; but with different
combinations of dependencies and interpreters.

- "make check-minreqs" Run tests specifically under our oldest supported
  Python and our oldest supported dependencies. This is the test that
  runs on GitLab as "check-python-minreqs". This helps ensure we do not
  regress support on older platforms accidentally.

- "make check-tox" Runs the tests under the newest supported
  dependencies, but under each supported version of Python in turn. At
  time of writing, this is Python 3.8 to 3.13 inclusive. This test helps
  catch bleeding-edge problems before they become problems for developer
  workstations. This is the GitLab test "check-python-tox" and is an
  optionally run, may-fail test due to the unpredictable nature of new
  dependencies being released into the ecosystem that may cause
  regressions.

- "make check-dev" Runs the tests under the newest supported
  dependencies using whatever version of Python the user happens to have
  installed. This is a quick convenience check that does not map to any
  particular GitLab test.

  (Note! check-dev may be busted on Fedora 41 and bleeding edge versions
  of setuptools. That's unrelated to this patch and I'll address it
  separately and soon. Thank you for your patience, --mgmt)

Finally, finally, finally: this means that QAPI tooling will be linted
and type-checked from the GitLab pipelines.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20250604200354.459501-5-jsnow@redhat.com
[Edited license choice per review --js]
Signed-off-by: John Snow <jsnow@redhat.com>