Upgrade `RustPython` to access ranged names (#5194)
## Summary
In https://github.com/astral-sh/RustPython-Parser/pull/8, we modified
RustPython to include ranges for any identifiers that aren't
`Expr::Name` (which already has an identifier).
For example, the `e` in `except ValueError as e` was previously
un-ranged. To extract its range, we had to do some lexing of our own.
This change should improve performance and let us remove a bunch of
code.
## Test Plan
`cargo test`
