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/error.rs

@@ -79,12 +79,12 @@ impl fmt::Debug for Error {
 impl std::error::Error for Error {
 	fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
 		match self {
-			Error::Io(ref err) => Some(err),
-			Error::Client(ref err) => Some(err),
-			Error::DuplicateBootnode { .. } => None,
-			Error::Prometheus(ref err) => Some(err),
-			Error::AddressesForAnotherTransport { .. } => None,
-			Error::DuplicateRequestResponseProtocol { .. } => None,
+			Self::Io(ref err) => Some(err),
+			Self::Client(ref err) => Some(err),
+			Self::Prometheus(ref err) => Some(err),
+			Self::DuplicateBootnode { .. } |
+			Self::AddressesForAnotherTransport { .. } |
+			Self::DuplicateRequestResponseProtocol { .. } => None,
 		}
 	}
 }