Contracts: Refactor test builder (#4158)

- Moved `substrate/frame/contracts/src/tests/builder.rs` into a pub
test_utils module, so we can use that in the
`pallet-contracts-mock-network` tests
- Refactor xcm tests to use XCM builders, and simplify the use case for
xcm-send

substrate/frame/contracts/src/test_utils.rs

@@ -0,0 +1,30 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Shared utilities for testing contracts.
+//! This is not part of the tests module because it is made public for other crates to use.
+#![cfg(feature = "std")]
+use frame_support::weights::Weight;
+pub use sp_runtime::AccountId32;
+
+pub const ALICE: AccountId32 = AccountId32::new([1u8; 32]);
+pub const BOB: AccountId32 = AccountId32::new([2u8; 32]);
+pub const CHARLIE: AccountId32 = AccountId32::new([3u8; 32]);
+pub const DJANGO: AccountId32 = AccountId32::new([4u8; 32]);
+
+pub const GAS_LIMIT: Weight = Weight::from_parts(100_000_000_000, 3 * 1024 * 1024);
+pub mod builder;