decl_module! macro: use 'frame_system' instead of system as default ident (#6500)

* Use frame_system as default ident.

* Remove unused 'frame_system' to 'system' renaming.

* Fix construct_runtime_ui tests.

* Rename system to frame_system in sudo/utility pallet test.

* Bump runtime impl_version.

* Update formatting.

substrate/frame/support/procedural/src/construct_runtime/mod.rs

@@ -59,7 +59,7 @@ fn construct_runtime_parsed(definition: RuntimeDefinition) -> Result<TokenStream
 			return Err(syn::Error::new(
 				modules_token.span,
 				"`System` module declaration is missing. \
-				 Please add this line: `System: system::{Module, Call, Storage, Config, Event<T>},`",
+				 Please add this line: `System: frame_system::{Module, Call, Storage, Config, Event<T>},`",
 			))
 		}
 	};