Fuzz Test Circuits by checking constraint satisfication instead of constructing proofs

[cronokirby]

Right now, we have tests that look like:

construct circuit
generate proof
assert!(proof.verify)

instead, we could simply check that the constraints of the circuit are satisfied by the witness, without actually doing the expensive part of constructing a Groth16 proof. This will speed up the test allowing us to cover more fuzz-space.

[PatStiles]

Interested in trying this out if its open for external contribution!

[redshiftzero]

we have implemented this, see #3583 for reference