[Proposal] Sequencer Selection: Fernet

IIRC, we had ruled out based sequencing since it doesn’t promote much diversity for L2 sequencers. Seems like incentives would lead to just a handful of builder-proposers pushing the blocks to L1 via a MEV sidecar. And if these go down it could affect L2 liveness.

@cooper-aztecLabs @jaosef do you remember if we had other reasons to not go with pure L1 based sequencing?