Emit log on Runtime Code change. (#9580)

* Emit digest item on Runtime Code changes.

* Add tests.

* cargo +nightly fmt --all

* Rename.

* Add comment.

* Move generic parameter to the trait.

* cargo +nightly fmt --all

* Elaborate in doc.

* Revert to RuntimeUpdated name

* cargo +nightly fmt --all

* Rename to RuntimeEnvironmentUpdated

substrate/frame/system/src/tests.rs

@@ -390,11 +390,24 @@ fn set_code_checks_works() {
 		ext.execute_with(|| {
 			let res = System::set_code(RawOrigin::Root.into(), vec![1, 2, 3, 4]);
 
+			assert_runtime_updated_digest(if res.is_ok() { 1 } else { 0 });
 			assert_eq!(expected.map_err(DispatchErrorWithPostInfo::from), res);
 		});
 	}
 }
 
+fn assert_runtime_updated_digest(num: usize) {
+	assert_eq!(
+		System::digest()
+			.logs
+			.into_iter()
+			.filter(|item| *item == generic::DigestItem::RuntimeEnvironmentUpdated)
+			.count(),
+		num,
+		"Incorrect number of Runtime Updated digest items",
+	);
+}
+
 #[test]
 fn set_code_with_real_wasm_blob() {
 	let executor = substrate_test_runtime_client::new_native_executor();
@@ -478,3 +491,12 @@ fn extrinsics_root_is_calculated_correctly() {
 		assert_eq!(ext_root, *header.extrinsics_root());
 	});
 }
+
+#[test]
+fn runtime_updated_digest_emitted_when_heap_pages_changed() {
+	new_test_ext().execute_with(|| {
+		System::initialize(&1, &[0u8; 32].into(), &Default::default(), InitKind::Full);
+		System::set_heap_pages(RawOrigin::Root.into(), 5).unwrap();
+		assert_runtime_updated_digest(1);
+	});
+}