Rework the event system of sc-network (#1370)

This commit introduces a new concept called `NotificationService` which
allows Polkadot protocols to communicate with the underlying
notification protocol implementation directly, without routing events
through `NetworkWorker`. This implies that each protocol has its own
service which it uses to communicate with remote peers and that each
`NotificationService` is unique with respect to the underlying
notification protocol, meaning `NotificationService` for the transaction
protocol can only be used to send and receive transaction-related
notifications.

The `NotificationService` concept introduces two additional benefits:
  * allow protocols to start using custom handshakes
  * allow protocols to accept/reject inbound peers

Previously the validation of inbound connections was solely the
responsibility of `ProtocolController`. This caused issues with light
peers and `SyncingEngine` as `ProtocolController` would accept more
peers than `SyncingEngine` could accept which caused peers to have
differing views of their own states. `SyncingEngine` would reject excess
peers but these rejections were not properly communicated to those peers
causing them to assume that they were accepted.

With `NotificationService`, the local handshake is not sent to remote
peer if peer is rejected which allows it to detect that it was rejected.

This commit also deprecates the use of `NetworkEventStream` for all
notification-related events and going forward only DHT events are
provided through `NetworkEventStream`. If protocols wish to follow each
other's events, they must introduce additional abtractions, as is done
for GRANDPA and transactions protocols by following the syncing protocol
through `SyncEventStream`.

Fixes https://github.com/paritytech/polkadot-sdk/issues/512
Fixes https://github.com/paritytech/polkadot-sdk/issues/514
Fixes https://github.com/paritytech/polkadot-sdk/issues/515
Fixes https://github.com/paritytech/polkadot-sdk/issues/554
Fixes https://github.com/paritytech/polkadot-sdk/issues/556

---
These changes are transferred from
https://github.com/paritytech/substrate/pull/14197 but there are no
functional changes compared to that PR

---------

Co-authored-by: Dmitry Markin <dmitry@markin.tech>
Co-authored-by: Alexandru Vasile <60601340+lexnv@users.noreply.github.com>

substrate/client/service/src/builder.rs

@@ -753,6 +753,11 @@ where
 	}
 
 	let protocol_id = config.protocol_id();
+	let genesis_hash = client
+		.block_hash(0u32.into())
+		.ok()
+		.flatten()
+		.expect("Genesis block exists; qed");
 
 	let block_announce_validator = if let Some(f) = block_announce_validator_builder {
 		f(client.clone())
@@ -802,11 +807,7 @@ where
 			// Allow both outgoing and incoming requests.
 			let (handler, protocol_config) = WarpSyncRequestHandler::new(
 				protocol_id.clone(),
-				client
-					.block_hash(0u32.into())
-					.ok()
-					.flatten()
-					.expect("Genesis block exists; qed"),
+				genesis_hash,
 				config.chain_spec.fork_id(),
 				warp_with_provider.clone(),
 			);
@@ -845,17 +846,13 @@ where
 	}
 
 	// create transactions protocol and add it to the list of supported protocols of
-	// `network_params`
-	let transactions_handler_proto = sc_network_transactions::TransactionsHandlerPrototype::new(
-		protocol_id.clone(),
-		client
-			.block_hash(0u32.into())
-			.ok()
-			.flatten()
-			.expect("Genesis block exists; qed"),
-		config.chain_spec.fork_id(),
-	);
-	net_config.add_notification_protocol(transactions_handler_proto.set_config());
+	let (transactions_handler_proto, transactions_config) =
+		sc_network_transactions::TransactionsHandlerPrototype::new(
+			protocol_id.clone(),
+			genesis_hash,
+			config.chain_spec.fork_id(),
+		);
+	net_config.add_notification_protocol(transactions_config);
 
 	// Create `PeerStore` and initialize it with bootnode peer ids.
 	let peer_store = PeerStore::new(
@@ -869,7 +866,6 @@ where
 	let peer_store_handle = peer_store.handle();
 	spawn_handle.spawn("peer-store", Some("networking"), peer_store.run());
 
-	let (tx, rx) = sc_utils::mpsc::tracing_unbounded("mpsc_syncing_engine_protocol", 100_000);
 	let (engine, sync_service, block_announce_config) = SyncingEngine::new(
 		Roles::from(&config.role),
 		client.clone(),
@@ -884,7 +880,7 @@ where
 		block_downloader,
 		state_request_protocol_name,
 		warp_request_protocol_name,
-		rx,
+		peer_store_handle.clone(),
 	)?;
 	let sync_service_import_queue = sync_service.clone();
 	let sync_service = Arc::new(sync_service);
@@ -905,7 +901,6 @@ where
 		fork_id: config.chain_spec.fork_id().map(ToOwned::to_owned),
 		metrics_registry: config.prometheus_config.as_ref().map(|config| config.registry.clone()),
 		block_announce_config,
-		tx,
 	};
 
 	let has_bootnodes = !network_params.network_config.network_config.boot_nodes.is_empty();