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/integration-tests/src/codegen/mod.rs

@@ -0,0 +1,26 @@
+// 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/>.
+
+/// Checks that code generated by `subxt-cli codegen` compiles. Allows inspection of compiler errors
+/// directly, more accurately than via the macro and `cargo expand`.
+///
+/// Generate by:
+///
+/// - run `polkadot --dev --tmp` node locally
+/// - `cargo run --release -p subxt-cli -- codegen | rustfmt > integration-tests/src/codegen/polkadot.rs`
+#[rustfmt::skip]
+#[allow(clippy::all)]
+mod polkadot;