Allow overriding pydocstyle convention rules (#8586)
## Summary
This fixes #2606 by moving where we apply the convention ignores --
instead of applying that at the very end, e track, we now track which
rules have been specifically enabled (via `Specificity::Rule`). If they
have, then we do *not* apply the docstring overrides at the end.
## Test Plan
Added unit tests to `ruff_workspace` and an integration test to
`ruff_cli`
