Implement status v2 version (#7590)

N/A


  Implements status v2 as defined in https://github.com/ethereum/consensus-specs/pull/4374/

beacon_node/lighthouse_network/src/peer_manager/peerdb.rs

@@ -746,6 +746,7 @@ impl<E: EthSpec> PeerDB<E> {
                     head_root: Hash256::ZERO,
                     finalized_epoch: Epoch::new(0),
                     finalized_root: Hash256::ZERO,
+                    earliest_available_slot: Some(Slot::new(0)),
                 },
             },
         );