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/src/exec.rs

@@ -18,6 +18,7 @@
 use crate::{
 	debug::{CallInterceptor, CallSpan, Tracing},
 	gas::GasMeter,
+	primitives::{ExecReturnValue, StorageDeposit},
 	storage::{self, meter::Diff, WriteOutcome},
 	BalanceOf, CodeHash, CodeInfo, CodeInfoOf, Config, ContractInfo, ContractInfoOf,
 	DebugBufferVec, Determinism, Error, Event, Nonce, Origin, Pallet as Contracts, Schedule,
@@ -37,7 +38,6 @@ use frame_support::{
 	Blake2_128Concat, BoundedVec, StorageHasher,
 };
 use frame_system::{pallet_prelude::BlockNumberFor, RawOrigin};
-use pallet_contracts_primitives::{ExecReturnValue, StorageDeposit};
 use smallvec::{Array, SmallVec};
 use sp_core::{
 	ecdsa::Public as ECDSAPublic,
@@ -1618,7 +1618,7 @@ mod tests {
 	use codec::{Decode, Encode};
 	use frame_support::{assert_err, assert_ok, parameter_types};
 	use frame_system::{EventRecord, Phase};
-	use pallet_contracts_primitives::ReturnFlags;
+	use pallet_contracts_uapi::ReturnFlags;
 	use pretty_assertions::assert_eq;
 	use sp_runtime::{traits::Hash, DispatchError};
 	use std::{cell::RefCell, collections::hash_map::HashMap, rc::Rc};