gen4: Subquery dependencies update

[systay]

Description

The way our semantic analysis works was causing problems for the plan building. Two different problems are solved by this changeset:

1. Rewriting away subqueries did not update the binding information, so even when a subquery was removed from the query, the binding information was not updated.
2. Dependencies from inside the subquery were leaking out. A small example will help illustrate the problem:

select (select col from foo), baz from bar 

The col on the inside of the subquery has a dependency on foo. This was leaking out so that the subquery expression also had a dependency to foo, when it really shouldn't.

Related Issue(s)

#7280

[GuptaManan100]

LGTM now! 🌀