fix(parser): prioritize parsing parenthesized expressions as Tuple when multi-expression CSV exists - #7807

When parsing parenthesized expressions where the first item is a subquery (e.g. ((SELECT 42), 1)), the parser's _parse_paren method matches the isinstance(this, (exp.Subquery, exp.Values)) check first and constructs a Subquery object, dropping subsequent items (such as , 1).

This PR fixes this by checking if the CSV contains multiple expressions (i.e., len(expressions) > 1 or a trailing comma) first, which constructs an exp.Tuple and correctly preserves all elements.

I have added a unit test verifying that ((SELECT 42), 1) parses as a Tuple successfully.

Closes #7805