Move test crates into a "testing" folder and add a ui (trybuild) test and ui-test helpers (#567)

* move test crates into a testing folder and add a ui test and helpers

* undo wee mixup with another PR

* cargo fmt

* clippy

* tidy ui-tests a little

* test different DispatchError types

* refactor dispatch error stuff

* name ui tests

* duff => useless

* align versions and cargo fmt

testing/ui-tests/src/dispatch_errors.rs

@@ -0,0 +1,39 @@
+// Copyright 2019-2022 Parity Technologies (UK) Ltd.
+// This file is part of subxt.
+//
+// subxt is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// subxt is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with subxt.  If not, see <http://www.gnu.org/licenses/>.
+
+use crate::utils::{
+    dispatch_error::{
+        ArrayDispatchError,
+        LegacyDispatchError,
+        NamedFieldDispatchError,
+    },
+    generate_metadata_from_pallets_custom_dispatch_error,
+};
+use frame_metadata::RuntimeMetadataPrefixed;
+
+pub fn metadata_array_dispatch_error() -> RuntimeMetadataPrefixed {
+    generate_metadata_from_pallets_custom_dispatch_error::<ArrayDispatchError>(vec![])
+}
+
+pub fn metadata_legacy_dispatch_error() -> RuntimeMetadataPrefixed {
+    generate_metadata_from_pallets_custom_dispatch_error::<LegacyDispatchError>(vec![])
+}
+
+pub fn metadata_named_field_dispatch_error() -> RuntimeMetadataPrefixed {
+    generate_metadata_from_pallets_custom_dispatch_error::<NamedFieldDispatchError>(
+        vec![],
+    )
+}