Support DISTINCT with correlated subqueries

### Problem Statement

The script below fails with `UnsupportedFeatureException[Cannot use correlated subquery in GROUP BY clause]`

```sql
CREATE TABLE tbl1 (a TEXT,fk INTEGER);
INSERT INTO tbl1 VALUES ('abc',1);
REFRESH TABLE tbl1;

CREATE TABLE tbl2 (id INTEGER,b TEXT);
INSERT INTO tbl2 VALUES (1,'def');
REFRESH TABLE tbl2;

SELECT DISTINCT a
,( SELECT b
FROM tbl2
WHERE id = fk
)
FROM tbl1;
```

### Possible Solutions

Support this as in PostgreSQL

```
postgres=# select distinct a,(select b from tbl2 where id=fk)
postgres-# from tbl1;
a | b
-----+-----
abc | def
(1 row)
```

### Considered Alternatives

- Storing the results in a "temporary" table then run the `DISTINCT` on it
- Use JOINs