IntegrityTest implementation should be feature gated (#13094)

* `IntegrityTest` implementation should be feature gated

The initial implementation for the old declarative macros is still feature gating the
implementation. As we only call this in a test, there is no need to have this compiled for wasm.

* Don't assume that all "consumers" have a `std` feature

substrate/frame/support/procedural/src/pallet/expand/hooks.rs

@@ -191,16 +191,19 @@ pub fn expand_hooks(def: &mut Def) -> proc_macro2::TokenStream {
 			}
 		}
 
-		impl<#type_impl_gen>
-			#frame_support::traits::IntegrityTest
+		// Integrity tests are only required for when `std` is enabled.
+		#frame_support::std_enabled! {
+			impl<#type_impl_gen>
+				#frame_support::traits::IntegrityTest
 			for #pallet_ident<#type_use_gen> #where_clause
-		{
-			fn integrity_test() {
-				<
-					Self as #frame_support::traits::Hooks<
+			{
+				fn integrity_test() {
+					<
+						Self as #frame_support::traits::Hooks<
 						<T as #frame_system::Config>::BlockNumber
-					>
-				>::integrity_test()
+						>
+						>::integrity_test()
+				}
 			}
 		}