Support builder spec

[terencechain]

Background

We want to support builder spec v0.2.1. The builder API will be implemented by both EL and CL clients that wish to participate in a builder network. Large number of validators will rely on this interface to extract MEV so it's important CLs integrate this spec. Without it, it could affect network share negatively as validators will seek to CL clients with better economics

Requirements

• New builder service
  • http client to call builder api
• Add builder healthz monitoring
  • Other services should aware when a builder is down
  • Poll builder_status
• Implement builder APIs
  • builder_status
  • builder_registerValidatorV1
    • beacon node support
    • validator client support
  • builder_getHeaderV1
  • builder_getPayloadV1
• Utililize parallsell calls to engine_getPayload and builder_getHeaderV1 for fallback
• Disallow builder usage until first finalized epoch post TTD
• Add new cli endpoint to specify builder endpoint
• Enhanced loggings
• Enhance metrics
• Validate SignedBuilderBid
• Log and check MEV rewards
• How should we prune registration objects in DB?

Beacon Node

• support new Beacon API Add register_validator endpoint ethereum/beacon-APIs#209

Validator Client

• support new Beacon API Add register_validator endpoint ethereum/beacon-APIs#209
• Must provide signed data (should cache them to avoid resigning every epoch). Related ref: https://github.com/ethereum/consensus-specs/pull/2884Reference: Add Builder API ethereum/execution-apis#209
• Update proposer settings file to mirror teku PR, teku PR2

[james-prysm]

Open questions

• how do we want to support web3signer/remote signer on this new API
• what new CLI flags are we adding to support this feature?
• how do we want to pass this new information to our service?
• should we extend our existing fee recipient flags/json interface or introduce new flags to handle additional information needed.