ultra sound money: optimistic relay

The default branch of this repo, called prod-optimistic-relaying is the modification of https://github.com/flashbots/mev-boost-relay to enable optimistic relaying for the ultra sound relay.

We have also opened a PR with the same set of changes on the main repo flashbots#285 to (a) help see the diff from the base relay implementation, (b) maintain the history of the change discussed in that PR, and (c) continue the discussion of upstreaming this change.

Operational documentation

see docs/optmistic for the following:

• Builder onboarding
• Event log
• An optimistic weekend