[pylint] - implement R0202 and R0203 with autofixes (#8335)
## Summary
Implements
[`no-classmethod-decorator`/`R0202`](https://pylint.readthedocs.io/en/latest/user_guide/messages/refactor/no-classmethod-decorator.html)
and
[`no-staticmethod-decorator`/`R0203`](https://pylint.readthedocs.io/en/latest/user_guide/messages/refactor/no-staticmethod-decorator.html)
with autofixes.
They're similar enough that all code is reusable for both.
See: #970
## Test Plan
`cargo test`
