The `BlobSidecar` construction has been moved to the relay and is no longer done by the BN / VC in blinded flow. Builder bid contents have been shrinked from full `BlindedBlobBundle` to `blob_kzg_commitments`. - https://github.com/ethereum/builder-specs/pull/90 - https://github.com/ethereum/beacon-APIs/pull/369
* Implement local validator block proposals * Address review feedback * Fix rebase issue