## Summary
This PR adds an autofix for the newly added PYI058 rule (added in
#9313). ~~The PR's current implementation is that the fix is only
available if the fully qualified name of `Generator` or `AsyncGenerator`
is being used:~~
- ~~`-> typing.Generator` is converted to `-> typing.Iterator`;~~
- ~~`-> collections.abc.AsyncGenerator[str, Any]` is converted to `->
collections.abc.AsyncIterator[str]`;~~
- ~~but `-> Generator` is _not_ converted to `-> Iterator`. (It would
require more work to figure out if `Iterator` was already imported or
not. And if it wasn't, where should we import it from? `typing`,
`typing_extensions`, or `collections.abc`? It seems much more
complicated.)~~
The fix is marked as always safe for `__iter__` or `__aiter__` methods
in `.pyi` files, but unsafe for all such methods in `.py` files that
have more than one statement in the method body.
This felt slightly fiddly to accomplish, but I couldn't _see_ any
utilities in
https://github.com/astral-sh/ruff/tree/main/crates/ruff_linter/src/fix
that would have made it simpler to implement. Lmk if I'm missing
something, though -- my first time implementing an autofix! :)
## Test Plan
`cargo test` / `cargo insta review`.
## Summary
This PR implements Y058 from flake8-pyi -- this is a new flake8-pyi rule
that was released as part of `flake8-pyi 23.11.0`. I've followed the
Python implementation as closely as possible (see
858c0918a8),
except that for the Ruff version, the rule also applies to `.py` files
as well as for `.pyi` files. (For `.py` files, we only emit the
diagnostic in very specific situations, however, as there's a much
higher likelihood of emitting false positives when applying this rule to
a `.py` file.)
## Test Plan
`cargo test`/`cargo insta review`
