Add syntax error for empty type parameter list (#12030)

## Summary

(I'm pretty sure I added this in the parser re-write but must've got
lost in the rebase?)

This PR raises a syntax error if the type parameter list is empty.

As per the grammar, there should be at least one type parameter:
```
type_params: 
    | invalid_type_params
    | '[' type_param_seq ']' 

type_param_seq: ','.type_param+ [','] 
```

Verified via the builtin `ast` module as well:
```console    
$ python3.13 -m ast parser/_.py
Traceback (most recent call last):
  [..]
  File "parser/_.py", line 1
    def foo[]():
            ^
SyntaxError: Type parameter list cannot be empty
```

## Test Plan

Add inline test cases and update the snapshots.

crates/ruff_python_parser/src/parser/statement.rs

@@ -3027,6 +3027,14 @@ impl<'src> Parser<'src> {
             Parser::parse_type_param,
         );
 
+        if type_params.is_empty() {
+            // test_err type_params_empty
+            // def foo[]():
+            //     pass
+            // type ListOrSet[] = list | set
+            self.add_error(ParseErrorType::EmptyTypeParams, self.current_token_range());
+        }
+
         self.expect(TokenKind::Rsqb);
 
         ast::TypeParams {