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`

crates/ruff_python_ast/src/source_code/generator.rs

@@ -1191,7 +1191,7 @@ impl<'a> Generator<'a> {
                 self.p("*");
                 self.unparse_expr(value, precedence::MAX);
             }
-            Expr::Name(ast::ExprName { id, .. }) => self.p_id(id),
+            Expr::Name(ast::ExprName { id, .. }) => self.p(id.as_str()),
             Expr::List(ast::ExprList { elts, .. }) => {
                 self.p("[");
                 let mut first = true;