Tools to test JuMP models

[odow]

I really think we need a tool that can test formulations (and reformulations) are equivalent.

See, e.g., jump-dev/MathOptInterface.jl#2416 (comment).

We currently have primal_feasibility_report, so perhaps we could hijack that to add some test cases. And if you provide partial (in)feasible starts, we could use a solver to fill in the blanks.

I can't immediately find the links, but I think we've discussed this before...