Replace flake8 with ruff

[fpgmaas]

Is your feature request related to a problem? Please describe.

I would like to propose to change flake8 with ruff. I have been quite annoyed with flake8, mainly because of the lack of support for configuration through pyproject.toml, or e.g. this issue.

ruff is a new tool that looks quite promising, that mentions it is "0-100x faster than existing linters". (Coincidentally, the homepage mentions that ruff is also used by Saleor, the main author of which recently opened an issue within deptry.)

My proposal would be to run flake8 and ruff in parallel for a while, and see if it happens often that ruff misses an issue that flake8 would have caught. If we are satisfied with ruff's performance, we can remove flake8.