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/bin/node/runtime/Cargo.toml

@@ -74,7 +74,6 @@ pallet-broker = { path = "../../../frame/broker", default-features = false}
 pallet-child-bounties = { path = "../../../frame/child-bounties", default-features = false}
 pallet-collective = { path = "../../../frame/collective", default-features = false}
 pallet-contracts = { path = "../../../frame/contracts", default-features = false}
-pallet-contracts-primitives = { path = "../../../frame/contracts/primitives", default-features = false}
 pallet-conviction-voting = { path = "../../../frame/conviction-voting", default-features = false}
 pallet-core-fellowship = { path = "../../../frame/core-fellowship", default-features = false}
 pallet-democracy = { path = "../../../frame/democracy", default-features = false}
@@ -171,7 +170,6 @@ std = [
 	"pallet-broker/std",
 	"pallet-child-bounties/std",
 	"pallet-collective/std",
-	"pallet-contracts-primitives/std",
 	"pallet-contracts/std",
 	"pallet-conviction-voting/std",
 	"pallet-core-fellowship/std",