Batch messages to network bridge and introduce a timeout to SubsystemContext::send_message (#2197)

* guide: batch network messages

* bridge: batch

* av-dist: batch outgoing messages

* time-out message sends in subsystem context

* Update node/subsystem/src/messages.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Revert "time-out message sends in subsystem context"

This reverts commit d49be62557ec37c8a350b93718acad723df704ef.

* Update node/network/availability-distribution/src/lib.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

polkadot/node/subsystem/src/messages.rs

@@ -203,6 +203,12 @@ pub enum NetworkBridgeMessage {
 	/// Send a message to one or more peers on the collation peer-set.
 	SendCollationMessage(Vec<PeerId>, protocol_v1::CollationProtocol),
 
+	/// Send a batch of validation messages.
+	SendValidationMessages(Vec<(Vec<PeerId>, protocol_v1::ValidationProtocol)>),
+
+	/// Send a batch of collation messages.
+	SendCollationMessages(Vec<(Vec<PeerId>, protocol_v1::CollationProtocol)>),
+
 	/// Connect to peers who represent the given `validator_ids`.
 	///
 	/// Also ask the network to stay connected to these peers at least
@@ -225,6 +231,8 @@ impl NetworkBridgeMessage {
 			Self::ReportPeer(_, _) => None,
 			Self::SendValidationMessage(_, _) => None,
 			Self::SendCollationMessage(_, _) => None,
+			Self::SendValidationMessages(_) => None,
+			Self::SendCollationMessages(_) => None,
 			Self::ConnectToValidators { .. } => None,
 		}
 	}