In the ruff config file added in #6954 explicitly selecting the ruff
rules to check was missed, resulting in ruff only checking a very small
subset of its available rules. That hasn't been desired, so this is the
first of a series of commits enabling more rules. In this PR all rules
whose violations can be either automatically fixed by ruff or are
trivial to fix manually get enabled. For the follow up PRs it's intended
to focus on one area of rules per PR to gradually improve the Python
code quality.
