Support sending and receiving multiple Justifications (#8266)

* client/network: support sending multiple justifications

* network: flag support for multiple justifications in protobuf request

* Update client/network/src/protocol.rs

Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>

* network: update comment on protobuf field

Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>

substrate/client/network/src/protocol.rs

@@ -580,6 +580,11 @@ impl<B: BlockT> Protocol<B> {
 				} else {
 					None
 				},
+				justifications: if !block_data.justifications.is_empty() {
+					Some(DecodeAll::decode_all(&mut block_data.justifications.as_ref())?)
+				} else {
+					None
+				},
 			})
 		}).collect::<Result<Vec<_>, codec::Error>>();
 
@@ -908,6 +913,7 @@ impl<B: BlockT> Protocol<B> {
 						receipt: None,
 						message_queue: None,
 						justification: None,
+						justifications: None,
 					},
 				],
 			},
@@ -1123,6 +1129,7 @@ fn prepare_block_request<B: BlockT>(
 		to_block: request.to.map(|h| h.encode()).unwrap_or_default(),
 		direction: request.direction as i32,
 		max_blocks: request.max.unwrap_or(0),
+		support_multiple_justifications: true,
 	};
 
 	CustomMessageOutcome::BlockRequest {