feat: target ESLint v9

[Marsup]

This makes all rules and configs work with ESLint v9. I have not tried to keep it compatible with v8 as I'm not sure it's worth the effort. Some code (the rules) was automatically migrated by an eslint tool and is probably compatible with both versions though, so if we decide to keep backwards-compatibility, we probably just have to keep a duplicate of the old configs. As can be seen in lab's PR, I'm not sure how to properly handle the old .eslintignore behavior, so I went with passing it through labrc.

The CI will of course fail as it needs a compatible lab to work.