Define ss58 prefix inside the runtime (#7810)

* Add SS58Prefix type to the frame_system config trait

* Remove unused chain_id runtime interface

Author: athei

src/lib.rs

@@ -618,6 +618,7 @@ mod tests {
 		type OnNewAccount = ();
 		type OnKilledAccount = ();
 		type SystemWeightInfo = ();
+		type SS58Prefix = ();
 	}
 
 	type Balance = u64;