Contracts: use compiled rust tests (#2347)

see #2189

This PR does the following:
- Bring the user api functions into a new pallet-contracts-uapi (They
are currently defined in ink!
[here])(https://github.com/paritytech/ink/blob/master/crates/env/src/engine/on_chain/ext.rs)
- Add older api versions and unstable to the user api trait.
- Remove pallet-contracts-primitives and bring the types it defined in
uapi / pallet-contracts
- Add the infrastructure to build fixtures from Rust files and test it
works by replacing `dummy.wat` and `call.wat`
- Move all the doc from wasm/runtime.rs to pallet-contracts-uapi.

This will be done in a follow up:
- convert the rest of the test from .wat to rust
- bring risc-v uapi up to date with wasm
- finalize the uapi host fns, making sure everything is codegen from the
source host fns in pallet-contracts

---------

Co-authored-by: Alexander Theißen <alex.theissen@me.com>

substrate/frame/contracts/uapi/src/flags.rs

@@ -0,0 +1,73 @@
+// 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.
+
+use bitflags::bitflags;
+
+bitflags! {
+	/// Flags used by a contract to customize exit behaviour.
+	#[cfg_attr(feature = "scale", derive(scale::Encode, scale::Decode, scale_info::TypeInfo))]
+	pub struct ReturnFlags: u32 {
+		/// If this bit is set all changes made by the contract execution are rolled back.
+		const REVERT = 0x0000_0001;
+	}
+}
+
+bitflags! {
+	/// Flags used to change the behaviour of `seal_call` and `seal_delegate_call`.
+	pub struct CallFlags: u32 {
+		/// Forward the input of current function to the callee.
+		///
+		/// Supplied input pointers are ignored when set.
+		///
+		/// # Note
+		///
+		/// A forwarding call will consume the current contracts input. Any attempt to
+		/// access the input after this call returns will lead to [`Error::InputForwarded`].
+		/// It does not matter if this is due to calling `seal_input` or trying another
+		/// forwarding call. Consider using [`Self::CLONE_INPUT`] in order to preserve
+		/// the input.
+		const FORWARD_INPUT = 0b0000_0001;
+		/// Identical to [`Self::FORWARD_INPUT`] but without consuming the input.
+		///
+		/// This adds some additional weight costs to the call.
+		///
+		/// # Note
+		///
+		/// This implies [`Self::FORWARD_INPUT`] and takes precedence when both are set.
+		const CLONE_INPUT = 0b0000_0010;
+		/// Do not return from the call but rather return the result of the callee to the
+		/// callers caller.
+		///
+		/// # Note
+		///
+		/// This makes the current contract completely transparent to its caller by replacing
+		/// this contracts potential output by the callee ones. Any code after `seal_call`
+		/// can be safely considered unreachable.
+		const TAIL_CALL = 0b0000_0100;
+		/// Allow the callee to reenter into the current contract.
+		///
+		/// Without this flag any reentrancy into the current contract that originates from
+		/// the callee (or any of its callees) is denied. This includes the first callee:
+		/// You cannot call into yourself with this flag set.
+		///
+		/// # Note
+		///
+		/// For `seal_delegate_call` should be always unset, otherwise
+		/// [`Error::InvalidCallFlags`] is returned.
+		const ALLOW_REENTRY = 0b0000_1000;
+	}
+}