Remove cplex feature/use egg's native ILP extraction once it's merged

[gussmith23]

Max developed ILP extraction in egg, reimplementing a lot of the work in our ILP-based extraction. We should depend on that instead of our own hand-rolled code. We can also remove the dependency on CPLEX and use an open source solver which is more easily installed, though perhaps we can keep the option to use CPLEX. I'm fairly certain the ILP library he chose allows you to swap out ILP solvers.