Offloading KZG Proof Computation from the beacon node

[jimmygchen]

EIP change: ethereum/EIPs#9378
execution-api PR: ethereum/execution-apis#630

The exact spec change is still pending and under active discussion, below is a rough list of what needs to be done:

• Update code to assemble DataColumnSidecar:
  • Extend blobs
  • Use cell proofs from EL (no computaion)
• Update integration with EL getPayloadV5 and EL getBlobsV2
• GetBlobSidecar API
  • We no longer have the blob KZG proofs, may need a v2 to return cell proofs?

[jimmygchen]

Marked as blocked for now as spec change hasn't been finalised.

[jimmygchen]

@ethDreamer and I have started working on this as the spec seems to be getting close to finalised and geth already has an implementation.

[jimmygchen]

Completed in #7117 🎉