Improve query engine state management

[tylerwilding-wk]

There are some notable inefficiencies in the internal representations for query state. Several naive representations were experimented with, all of which had the potential to dominate execution time far beyond IO costs. However, there exist well-defined solutions that could be implemented to drastically reduce overall runtime of the query engine under many or most circumstances.

In particular, there are two elements of state that need improvement:

1. The manner in which variable bindings are stored eagerly evaluates all cross products, requiring repeated linear traversals over potentially tens or hundreds of thousands of immutable maps.
2. The manner in which the query engine tracks whether or not it has already evaluated a particular predicate.

To address (1), we intend to use or build a lazy relational algebra system - https://github.com/Workiva/lazy-tables

To address (2), we intend to explore feasible alternatives and choose one/more to implement.

The expectation is that we could drastically improve the query engine performance and possibly simplify several code paths.