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>

cumulus/parachains/runtimes/contracts/contracts-rococo/Cargo.toml

@@ -52,7 +52,6 @@ pallet-transaction-payment-rpc-runtime-api = { path = "../../../../../substrate/
 pallet-utility = { path = "../../../../../substrate/frame/utility", default-features = false}
 pallet-sudo = { path = "../../../../../substrate/frame/sudo", default-features = false}
 pallet-contracts = { path = "../../../../../substrate/frame/contracts", default-features = false}
-pallet-contracts-primitives = { path = "../../../../../substrate/frame/contracts/primitives", default-features = false}
 
 # Polkadot
 pallet-xcm = { path = "../../../../../polkadot/xcm/pallet-xcm", default-features = false }
@@ -102,7 +101,6 @@ std = [
 	"pallet-authorship/std",
 	"pallet-balances/std",
 	"pallet-collator-selection/std",
-	"pallet-contracts-primitives/std",
 	"pallet-contracts/std",
 	"pallet-insecure-randomness-collective-flip/std",
 	"pallet-message-queue/std",