Add payload attestation validator duty (#9178)

Co-Authored-By: Eitan Seri-Levi <eserilev@ucsc.edu>

Co-Authored-By: Jimmy Chen <jchen.tc@gmail.com>

validator_client/signing_method/src/web3signer.rs

@@ -21,6 +21,7 @@ pub enum MessageType {
     ValidatorRegistration,
     // TODO(gloas) verify w/ web3signer specs
     ExecutionPayloadEnvelope,
+    PayloadAttestation,
 }
 
 #[derive(Debug, PartialEq, Copy, Clone, Serialize)]
@@ -78,6 +79,7 @@ pub enum Web3SignerObject<'a, E: EthSpec, Payload: AbstractExecPayload<E>> {
     ContributionAndProof(&'a ContributionAndProof<E>),
     ValidatorRegistration(&'a ValidatorRegistrationData),
     ExecutionPayloadEnvelope(&'a ExecutionPayloadEnvelope<E>),
+    PayloadAttestationData(&'a PayloadAttestationData),
 }
 
 impl<'a, E: EthSpec, Payload: AbstractExecPayload<E>> Web3SignerObject<'a, E, Payload> {
@@ -144,6 +146,7 @@ impl<'a, E: EthSpec, Payload: AbstractExecPayload<E>> Web3SignerObject<'a, E, Pa
             }
             Web3SignerObject::ValidatorRegistration(_) => MessageType::ValidatorRegistration,
             Web3SignerObject::ExecutionPayloadEnvelope(_) => MessageType::ExecutionPayloadEnvelope,
+            Web3SignerObject::PayloadAttestationData(_) => MessageType::PayloadAttestation,
         }
     }
 }