Define ss58 prefix inside the runtime (#7810)

* Add SS58Prefix type to the frame_system config trait

* Remove unused chain_id runtime interface

substrate/test-utils/runtime/src/lib.rs

@@ -462,6 +462,7 @@ impl frame_system::Config for Runtime {
 	type OnNewAccount = ();
 	type OnKilledAccount = ();
 	type SystemWeightInfo = ();
+	type SS58Prefix = ();
 }
 
 impl pallet_timestamp::Config for Runtime {