Enable ruff SLOT linting rule

[brisvag]

References and relevant issues

Updating ruff linting rules is tracked by #5589.

Documentation for the SLOT linting rule can be found at: https://docs.astral.sh/ruff/rules/#flake8-slots-slot

Subclasses of str should define __slots__ Subclasses of tuple should define __slots__ Subclasses of {namedtuple_kind} should define __slots__

Description

The benefit of these rules is memory savings, because classes with __slots__ are more compact than classes with arbitrary attribute dictionaries. This is typically a small benefit, but could speed up some stuff like translations.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.38%. Comparing base (dec8b09) to head (892fa7b).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #6843 +/- ## ========================================== - Coverage 92.44% 92.38% -0.06% ========================================== Files 614 614 Lines 54830 54833 +3 ========================================== - Hits 50686 50660 -26 - Misses 4144 4173 +29 ```

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[jni]

I've updated the title and description. In general, before merging and/or applying the ready-to-merge label, it would be good to have more thorough descriptions like the above. Many of these rules are mysterious even to long-time Python developers 🙋😅.