This change brings geth into compliance with the current engine API
specification for the Prague fork. I have moved the assignment of
ExecutionPayloadEnvelope.Requests into BlockToExecutableData to ensure
there is a single place where the type is removed.
While doing so, I noticed that handling of requests in the miner was not
quite correct for the empty payload. It would return `nil` requests for
the empty payload even for blocks after the Prague fork. To fix this, I
have added the emptyRequests field in miner.Payload.
This PR adds an extra mechanism to sync.HeadSync that tries to retrieve the latest finality update from every server each time it sends an optimistic update in a new epoch (unless we already have a validated finality update attested in the same epoch).
Note that this is not necessary and does not happen if the new finality update is delivered before the optimistic update. The spec only mandates light_client_finality_update events when a new epoch is finalized. If the chain does not finalize for a while then we might need an explicit request that returns a finality proof that proves the same finality epoch from the latest attested epoch.
This adds support for the Deneb beacon chain fork, and fork handling
in general, to the beacon chain light client implementation.
Co-authored-by: Zsolt Felfoldi <zsfelfoldi@gmail.com>
