TST: migrate to official astral-sh/setup-uv action

[neutrinoceros]

TODO:

• adjust coverage configuration (I removed my --editable install hack)
• somehow replace uv pip list (maybe use concrete, pinned test dependencies ?)
• fix minimal env
• reinstate some form of --no-build (I don't think I can use it at a global level since gpgi itself needs building)

[neutrinoceros]

I think I found a bug in uv:

$ uvx -p 3.11 --with-requirements=requirements/tests.txt --resolution=lowest-direct coverage@latest run -m pytest -ra
⠙ Resolving dependencies...                                                                                                                          warning: The direct dependency `coverage` is unpinned. Consider setting a lower bound when using `--resolution-strategy lowest` to avoid using outdated versions.
⠹ coverage==3.0                                                                                                                                      error: Failed to download and build `coverage==3.0`
  Caused by: Build backend failed to determine extra requires with `build_wheel()` with exit status: 1
--- stdout:

--- stderr:
Traceback (most recent call last):
  File "<string>", line 14, in <module>
  File "/Users/clm/.cache/uv/builds-v0/.tmpn4BjM6/lib/python3.11/site-packages/setuptools/build_meta.py", line 332, in get_requires_for_build_wheel
    return self._get_build_requires(config_settings, requirements=[])
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/clm/.cache/uv/builds-v0/.tmpn4BjM6/lib/python3.11/site-packages/setuptools/build_meta.py", line 302, in _get_build_requires
    self.run_setup()
  File "/Users/clm/.cache/uv/builds-v0/.tmpn4BjM6/lib/python3.11/site-packages/setuptools/build_meta.py", line 503, in run_setup
    super().run_setup(setup_script=setup_script)
  File "/Users/clm/.cache/uv/builds-v0/.tmpn4BjM6/lib/python3.11/site-packages/setuptools/build_meta.py", line 318, in run_setup
    exec(code, locals())
  File "<string>", line 26, in <module>
  File "/Users/clm/.cache/uv/built-wheels-v3/pypi/coverage/3.0/jE2zyNBjKB6EdrlVZO6d9/coverage-3.0.tar.gz/ez_setup.py", line 98
    except pkg_resources.VersionConflict, e:
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
SyntaxError: multiple exception types must be parenthesized
---

I'll report upstream later.

update: reported as astral-sh/uv#7164