bug: BSB22 commitment in Groth16 is not overloaded when running only the solver

[ivokub]

So the commitment hint uses proving key which the solver doesn't have access to. When we run the prover then the prover overloads the hint with a function which has access to the proving key and then the solver has access to it to generate the full witness.

However, when we only run solver (in fuzzer/assertions etc.), then we do not overload and because the dummy commitment panics, the solver returns error. But actually the circuit may be solvable.

@Tabaie, @gbotrel