Do not add SINGLE_VALUE aggregate function to a sub-query that will never return more than one row

In the following query, the subquery is producing a scalar value but the logical plan still creates a SqlSingleValueAggFunction.

select r_regionkey from region
   where r_regionkey > (select min(n_regionkey) * 2 from nation);

If the aggregate is just min(n_regionkey) instead of the expression min(n_regionkey) * 2 then no SqlSingleValueAggFunction is created. Ideally, both should behave the same.

This is not necessarily a bug but it does create a burden on the underlying execution engine to support this function even in cases where it may not be needed.