fix(core): disable SingleDistinctToGroupBy for distinct aggregation unparsing

[goldmedal]

Description

Given a SQL using distinct aggregation

SELECT c_custkey, count(distinct c_name) FROM customer GROUP BY c_custkey

It will be planned to multiple aggregation plans by SingleDistinctToGroupBy like

     Projection: customer.c_custkey, count(DISTINCT customer.c_name)
      Projection: customer.c_custkey, count(alias1) AS count(DISTINCT customer.c_name)
        Aggregate: groupBy=[[customer.c_custkey]], aggr=[[count(alias1)]]
          Aggregate: groupBy=[[customer.c_custkey, customer.c_name AS alias1]], aggr=[[]]
            SubqueryAlias: customer
              Projection: customer.c_custkey, customer.c_name
                SubqueryAlias: customer
                  Projection: customer.c_custkey AS c_custkey, customer.c_name AS c_name
                    TableScan: customer

However, The unparser can't process it well. Disable it to get the simpler plan:

     Projection: customer.c_custkey, count(DISTINCT customer.c_name)
      Aggregate: groupBy=[[customer.c_custkey]], aggr=[[count(DISTINCT customer.c_name)]]
        SubqueryAlias: customer
          Projection: customer.c_custkey, customer.c_name
            SubqueryAlias: customer
              Projection: customer.c_custkey AS c_custkey, customer.c_name AS c_name
                TableScan: customer

[grieve54706]

LGTM