[WIP] Projection Push Down Join, Projection Remove, and Projection Agg Transpose Rules

[Sweetsuro]

DO NOT MERGE. This PR implements the remainder of the projection transpose series of rules.

List of Necessary Fixes Prior to Merge

• Projection Push Down Join Rule can still apply on the top-level proj -> join, even if it's just generating redundant projection nodes beneath the join node. Need to find a way to avoid applying the rule in cascade's core logic (and in heuristic code path).
• Join enumeration is not possible with cyclic memo nodes. Need to implement a better join enumeration algorithm that is not brute forcing through everything in the memo table.
• Need a way to match on Scan nodes. Currently, ProjectRemoveRule is only possible in the Heuristic Optimizer pass because of this.
• Projection Agg Transpose Rule remains unimplemented.

Projection Push Down Join Rule

• This rule pushes a projection past a join node. It may still have a top most projection node, and in most cases creates a projection node above the left join child and a projection node above the right join child.
• This rule is commented out but intended to be a heuristic wrapper rule

Projection Remove Rule

• This rule matches on a projection node followed by a scan node.
• It is added in the preliminary heuristic pass

Testing

Unit tests using the dummy heuristic optimizer were implemented.