EIP-4844 tracking

[protolambda]

This issue tracks open TODOs for EIP-4844 integration into the consensus-specs.

• Fork-choice spec
  • Define "dependency" system in fork-choice and testing. (need help from @djrtwo or @adiasg)
  • Move download-requirement of blobs from validator spec to fork-choice spec doc
• KZG commitments in BeaconState
  • Register the KZG commitments that are included in beacon-blocks in the BeaconState.
    This is optional, but provides more direct merkle proofs / access. Indirectly, through the beacon-block latest_header and history accumulators we already include them though.
• Update configs / presets files with new EIP-4844 variables
• Enable pyspec generation from EIP-4844 feature dir
• Update test-generators & py-tests to output beacon-chain test-vectors for this feature

And there's an option to move the process_blob_kzgs to under the is_execution_enabled if-statement, but it's a no-op on empty payloads (when execution is not enabled), and ideally we remove the if-statement in the next hardfork after Bellatrix.