Make the prover run the constraints

[joseandro]

• Mostly for soundness.
• Missing in the definition of the VM instructions: some of these are under-constrained.
• Task: perhaps start with a pass to identify these with TODO’s or FIXME’s, and then someone else can proceed implementing each of them.
• Danny can help suggesting what's under constrained.
• Does this need folding to be fully in place? Probably not. Apply the Expr framework to evaluate the constraints on the witness.

[emberian]

:+1:, this feature was hugely helpful during initial development of mina/snarky