Sequencer-side implementation for Optimistic Block

[itamarreif]

In order for the Auctioneer to drive optimistic block execution in Geth, it needs to receive a stream of optimistic blocks and block commitments. As described in the PR introducing this API:

The Auctioneer receives blocks optimistically from the sequencer in order to maximize the auction duration.

After a block is committed, the Auctioneer will submit the highest paying bundle for inclusion by the sequencer.

Optimistic Block Stream

1. The Sequencer will stream blocks to the Auctioneer optimistically, i.e. before they are finalized (ProcessProposal).
2. The Sequencer will also stream block commitments to the Auctioneer, which mark blocks as final thanks to CometBFT's single slot finality.

This functionality needs to be optional, as only one sequencer node in the network needs to be serving this stream (i.e. the sequencer node run alongside the Auctioneer, but not any of the ones connected to a Composer).

Tasks

Beta Give feedback

1. feat(proto): add bundle and optimistic block apis #1519
   auctioneer cd ci conductor docker proto sequencer +7
   
2. Implement the sequencer-side server for the optimistic block stream
3. Link to PR with the auctioneer-side implementation that uses the client for this

┆Issue Number: ENG-847