Replace flake8 and black with ruff

[berendkleinhaneveld]

Just noticed that ruff has a 0.1.* version out that includes a formatter that serves as a drop-in replacement for black.
Thought I'd try to apply it to this repo, see what it would entail to adopt it.

One thing I noticed is that the linter will not complain if something is wrong that could be solved by running the formatter, so in the pre-commit config and in the linting step in CI, I've added a step to check the formatting specifically.

[berendkleinhaneveld]

I got one more thing: I also wanted to checkout the default setting for import sorting, so I added a commit that does just that. I'm not sure I like the order much better, but on the other hand: as long as I don't have to order the imports by hand, I'm happy. What do you think?

And I also applied --fix on the linting step in pre-commit, so it mirrors the behaviour of the format step.

[Korijn]

I got one more thing: I also wanted to checkout the default setting for import sorting, so I added a commit that does just that. I'm not sure I like the order much better, but on the other hand: as long as I don't have to order the imports by hand, I'm happy. What do you think?

And I also applied --fix on the linting step in pre-commit, so it mirrors the behaviour of the format step.

The imports are still in three groups right? That's really what's most important to me. I want to be able to quickly see what standard library and third party dependencies are used. I don't care about the order within the groups.

Seems fine with me.