Goals:
In addition to traditional benchmarks, ensure that join optimization operates properly across different query complexities, scale factors and predicate selectivities

Deliverables:
Tooling to chart the join optimizer across scale factors and predicate selectivities (so-called Picasso diagrams) https://vldb.org/pvldb/vol3/D01.pdf
Extend the existing product_limits test suite to include join optimization
Ensure that spilling to disk is tested extensively
Ensure that nested $lookup is represented in the test suites