Allow pallet::call to return DispatchResult (#8241)

* allow dispatch result

* remove custom error message

* format

* add forgotten UI test

* fix test

* fix tests

substrate/frame/support/test/tests/pallet_ui/call_invalid_return.rs

@@ -0,0 +1,22 @@
+#[frame_support::pallet]
+mod pallet {
+	use frame_support::pallet_prelude::Hooks;
+	use frame_system::pallet_prelude::{BlockNumberFor, OriginFor};
+
+	#[pallet::config]
+	pub trait Config: frame_system::Config {}
+
+	#[pallet::pallet]
+	pub struct Pallet<T>(core::marker::PhantomData<T>);
+
+	#[pallet::hooks]
+	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {}
+
+	#[pallet::call]
+	impl<T: Config> Pallet<T> {
+		fn foo(origin: OriginFor<T>) -> ::DispatchResult { todo!() }
+	}
+}
+
+fn main() {
+}

substrate/frame/support/test/tests/pallet_ui/call_invalid_return.stderr

@@ -0,0 +1,5 @@
+error: expected `DispatchResultWithPostInfo` or `DispatchResult`
+  --> $DIR/call_invalid_return.rs:17:35
+   |
+17 |         fn foo(origin: OriginFor<T>) -> ::DispatchResult { todo!() }
+   |                                         ^^