Replace pylint + isort by ruff

[timobrembeck]

Motivation

Our CI workflows take quite a while, mostly due to the tests, but also pylint is taking a considerable amount of time. I think we could reduce this by migrating from pylint to ruff:

Proposed Solution

• Replace pylint and isort by ruff
• Check whether there's an automated tool which can migrate the pylint: disable= statements

Alternatives

Maybe it isn't worth the effort...

Additional Context

Pylint is not completely implemented by ruff yet (see https://github.com/astral-sh/ruff/issues/970), so we would loose a few rules (but also ruff has a lot of extra checks that pylint doesn't, mostly those of flake8)...