Add new RPC method to get the chain type (#5576)

* Add new RPC method to get the chain type

This adds a new RPC method to get the chain type of the running chain.
The chain type needs to be specified in the chain spec. This should make
it easier for tools/UI to display extra information without needing to
rely on parsing the chain name.

* Update client/rpc-api/src/system/mod.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Primitive crate

* Feedback

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

substrate/client/rpc/src/system/tests.rs

@@ -105,6 +105,7 @@ fn api<T: Into<Option<Status>>>(sync: T) -> System<Block> {
 		impl_version: "0.2.0".into(),
 		chain_name: "testchain".into(),
 		properties: Default::default(),
+		chain_type: Default::default(),
 	}, tx)
 }
 
@@ -117,7 +118,7 @@ fn wait_receiver<T>(rx: Receiver<T>) -> T {
 fn system_name_works() {
 	assert_eq!(
 		api(None).system_name().unwrap(),
-		"testclient".to_owned()
+		"testclient".to_owned(),
 	);
 }
 
@@ -125,7 +126,7 @@ fn system_name_works() {
 fn system_version_works() {
 	assert_eq!(
 		api(None).system_version().unwrap(),
-		"0.2.0".to_owned()
+		"0.2.0".to_owned(),
 	);
 }
 
@@ -133,7 +134,7 @@ fn system_version_works() {
 fn system_chain_works() {
 	assert_eq!(
 		api(None).system_chain().unwrap(),
-		"testchain".to_owned()
+		"testchain".to_owned(),
 	);
 }
 
@@ -141,7 +142,15 @@ fn system_chain_works() {
 fn system_properties_works() {
 	assert_eq!(
 		api(None).system_properties().unwrap(),
-		serde_json::map::Map::new()
+		serde_json::map::Map::new(),
+	);
+}
+
+#[test]
+fn system_type_works() {
+	assert_eq!(
+		api(None).system_type().unwrap(),
+		Default::default(),
 	);
 }