Rationale:

@yuval-illumex is trying to support parenthesized expressions like (a, b) in various places (see #390, and #391)

I believe these are more commonly called tuple or row types in postgres or trino. Rather than adding special case handling for parens in various places, it would be better to simply support parsing tuples in general

Changes

1. Support parsing tuple expressions in select statement
2. Tests for same
3. Remove special case added in Allow parentheses in GROUP BY #390 for distinct clause
4. Add tests in Support parentheses in DISTINCT clause, CURRENT_TIMESTAMP, CURRENT_TIME, and CURRENT_DATE #391 demonstrating this code can parse paren'd expressions in the group by

Reference:

This syntax is supported by postgres:

alamb=# select (1, 'foo');
   row   
---------
 (1,foo)
(1 row)

It is not supported by mysql:

mysql> select (1, 2);
ERROR 1241 (21000): Operand should contain 1 column(s)