Raise syntax error for unparenthesized generator expr in multi-argument call (#12445)

## Summary

This PR fixes a bug to raise a syntax error when an unparenthesized
generator expression is used as an argument to a call when there are
more than one argument.

For reference, the grammar is:
```
primary:
    | ...
    | primary genexp 
    | primary '(' [arguments] ')' 
    | ...

genexp:
    | '(' ( assignment_expression | expression !':=') for_if_clauses ')' 
```

The `genexp` requires the parenthesis as mentioned in the grammar. So,
the grammar for a call expression is either a name followed by a
generator expression or a name followed by a list of argument. In the
former case, the parenthesis are excluded because the generator
expression provides them while in the later case, the parenthesis are
explicitly provided for a list of arguments which means that the
generator expression requires it's own parenthesis.

This was discovered in https://github.com/astral-sh/ruff/issues/12420.

## Test Plan

Add test cases for valid and invalid syntax.

Make sure that the parser from CPython also raises this at the parsing
step:
```console
$ python3.13 -m ast parser/_.py
  File "parser/_.py", line 1
    total(1, 2, x for x in range(5), 6)
                ^^^^^^^^^^^^^^^^^^^
SyntaxError: Generator expression must be parenthesized

$ python3.13 -m ast parser/_.py
  File "parser/_.py", line 1
    sum(x for x in range(10), 10)
        ^^^^^^^^^^^^^^^^^^^^
SyntaxError: Generator expression must be parenthesized
```

crates/ruff_python_parser/src/parser/expression.rs

@@ -2272,9 +2272,10 @@ impl<'src> Parser<'src> {
         command
     }
 
-    /// Validate that the given arguments doesn't have any duplicate keyword argument.
-    ///
-    /// Report errors for all the duplicate names found.
+    /// Performs the following validations on the function call arguments:
+    /// 1. There aren't any duplicate keyword argument
+    /// 2. If there are more than one argument (positional or keyword), all generator expressions
+    ///    present should be parenthesized.
     fn validate_arguments(&mut self, arguments: &ast::Arguments) {
         let mut all_arg_names =
             FxHashSet::with_capacity_and_hasher(arguments.keywords.len(), FxBuildHasher);
@@ -2292,6 +2293,25 @@ impl<'src> Parser<'src> {
                 );
             }
         }
+
+        if arguments.len() > 1 {
+            for arg in arguments.args.iter() {
+                if let Some(ast::ExprGenerator {
+                    range,
+                    parenthesized: false,
+                    ..
+                }) = arg.as_generator_expr()
+                {
+                    // test_ok args_unparenthesized_generator
+                    // sum(x for x in range(10))
+
+                    // test_err args_unparenthesized_generator
+                    // sum(x for x in range(10), 5)
+                    // total(1, 2, x for x in range(5), 6)
+                    self.add_error(ParseErrorType::UnparenthesizedGeneratorExpression, range);
+                }
+            }
+        }
     }
 }