Improve circuit debugging with a MockProver approach a la Halo2

[CPerezz]

In Halo2 we have a fantastic tool for circuit-debugging purposes. The MockProver. It basically allows to check all the gate-constraints and Lookup errors returning a really accurated description of the error place and the values involved in it.

The idea is to do something similar. Which at the same time, aims to reduce testing-time since it does not actually perform any commitments or requires any setup.

See more details here: https://github.com/zcash/halo2/blob/d111807798d4719df36dc2b05b0104b69efdceb3/halo2_proofs/src/dev.rs#L465