Implement Consensus Component

[frisitano]

Overview

We should implement a component responsible for evaluating the consensus of new blocks. Initially, this will be a simple check to assert that the block originated from an authorized signer. Initially, we will have a static list of authorized signers. However, these signers can be rotated, so the rollup node should be aware of this. This rotation can be tracked by observing the authorized signer configuration on L1.