Clean up sc-network (#9761)

* Clean up sc-network

- Avoid using clone() for the Copy type `PeerId`.
- Use `find_map` for `filter_map` and `next`.
- Use `Self`.

* More on Copy types

* Cargo +nightly fmt --all

* More ..

* fmt

* Revert vec![default_notif_handshake_message]

substrate/client/network/src/service/out_events.rs

@@ -142,7 +142,7 @@ impl OutChannels {
 		let metrics =
 			if let Some(registry) = registry { Some(Metrics::register(registry)?) } else { None };
 
-		Ok(OutChannels { event_streams: Vec::new(), metrics: Arc::new(metrics) })
+		Ok(Self { event_streams: Vec::new(), metrics: Arc::new(metrics) })
 	}
 
 	/// Adds a new [`Sender`] to the collection.