Builder API: EIP-4844 and Capella changes

Changes will be required on both the beacon API and builder API.

Beacon API: proposed changes
Builder API: proposed changes

Image Not Showing Possible Reasons

The image file may be corrupted
The server hosting the image is unavailable
The image path is incorrect
The image format is not supported

Open questions

Does make sense to add a new submitBlindedBlockV2 endpoint, that includes blobs_sidecar in the response (SignedBeaconBlockAndBlobsSidecar).
- Chris (@metachris)
  
  from the discussions i've had with EF/CL peers, there seems to be a preference for reusing the existing API call, rather than introducing a new V2 one.
- Enrico (@tbenr)
  
  It makes sense to me to have a V2 returning the entire SignedBeaconBlockAndBlobsSidecar. It reduces complexity and the overhead is minimal since ExecutionPayload and BlobsSidecar are the biggest objects we need to get anyway.
- Alex (@ralexstokes)
  
  I think we should mirror the existing APIs and it seems like we can get away with just using the V1

Action items

Implement builder spec changes left to be done on lighthouse.
Generate test vectors.
Share test vectors with falshbots so they can test early and share potential issues with CL teams.

If you have any feedback you can reach @jimmygchen or @0xGabi.