✨ support correlated subqueries

[joocer]

trafficstars

Allow subqueries to reference values from the outer query.

[joocer]

If this can't be done by rewriting to a join, I'm not sure how to do this without running the sub query over and over again.

Naive plan may be to run and loop, Optimizer may rewrite as a join.

Not even sure how to write than in the naive plan.