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/test/src/block_import.rs

@@ -46,14 +46,14 @@ fn prepare_good_block() -> (TestClient, Hash, u64, PeerId, IncomingBlock<Block>)
 		client,
 		hash,
 		number,
-		peer_id.clone(),
+		peer_id,
 		IncomingBlock {
 			hash,
 			header,
 			body: Some(Vec::new()),
 			indexed_body: None,
 			justifications,
-			origin: Some(peer_id.clone()),
+			origin: Some(peer_id),
 			allow_missing_state: false,
 			import_existing: false,
 			state: None,