Get the correct number of connected peers in SyncState (#13700)

`Protocol` is not a reliable source for the information of connected
peers because it doesn't have real-time information of the actual
connectivity state because it's not resposible for accepting/rejecting
connections and gets that information with delay from `SyncinEngine`.

substrate/client/network/sync/src/engine.rs

@@ -711,7 +711,9 @@ where
 				ToServiceCommand::NewBestBlockImported(hash, number) =>
 					self.new_best_block_imported(hash, number),
 				ToServiceCommand::Status(tx) => {
-					let _ = tx.send(self.chain_sync.status());
+					let mut status = self.chain_sync.status();
+					status.num_connected_peers = self.peers.len() as u32;
+					let _ = tx.send(status);
 				},
 				ToServiceCommand::NumActivePeers(tx) => {
 					let _ = tx.send(self.chain_sync.num_active_peers());