BLD/STY: migrate to pyproject.toml and ruff

[jacopoabramo]

Tested build locally with tox -e pytest.

Many tests fail on my machine but I suspect this is due to the absence of the CI settings.

EDIT: since flake8 doesn't support PEP 518, this PR also substitutes black and flake8 with ruff

[jacopoabramo]

@tacaswell so apparently I discovered - with my surprise - that flake8 doesn't support PEP 518.

If it's ok with you I would want to merge this and then work on a new PR to swap flake8 with ruff. I could do this in the same PR if you're ok with it.

[tacaswell]

Can you fix the linting one way or another in this PR? I do want to merge this PR and then have every other PR be broken until we get the lining fixed.

I'm 👍 on switching to ruff, flake8 is not a reasonably maintained project.

[tacaswell]

The simplest thing is probably to drop the flake8 config in what ever file it wants and then remove it in a follow on PR.

[jacopoabramo]

I dropped flake8 from the .pre-commit-config.yaml, which is nice because it can be swapped with the pre-commit hook from astral-sh. Once tests are ok this can be merged.

[tacaswell]

I do not think turning off linting is the best option. It will mean that PRs that come in between this being merged and the linting being fixed will not be linted which means some changes that will flag it will creep in (for example my love of single quotes). Depending on sequencing this may lead to the CI on the commit changing the linter passing and then the main branch failing as soon as it is merged.

Can you please either move the flake8 config to someplace it will find it or move to ruff in this PR?

[jacopoabramo]

@tacaswell if I remember correctly, ruff default configuration is the same as black, so the same rules for isort should apply as well.