Add support for returning multiple joined tables

[piercefreeman]

Our previous table query generation relied on the start operator to retrieve all table fields. This worked for one return table (or for multiple tables with completely disjoint values) but failed as soon as values overlapped, as SQL would only return the last one in the ordering chain. We refactor our table selection to use a coupled table_column response to avoid this conflict and further update our casting pipeline to leverage it.