[protocol] enable more than one circuits to have multiple proofs per block

[dantaik]

As of now, we only require one proof (based on one circuit) to mark a block as "proven", maybe we can have 2 or 3 different circuits with different setups, then mark a block as "proven" only when there are 2/2 or 2/3 consistent proofs -- they all prove the block has the same block-hash.

We also need to suspend the chain if there are conflicting proofs.

See https://hackmd.io/@vbuterin/zk_slides_20221010 by Vitalik.