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/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "pallet-contracts-uapi"
+version = "4.0.0-dev"
+authors.workspace = true
+edition.workspace = true
+license = "Apache-2.0"
+homepage = "https://substrate.io"
+repository.workspace = true
+description = "Exposes all the host functions that a contract can import."
+
+[dependencies]
+paste = { version = "1.0", default-features = false }
+bitflags = "1.0"
+scale-info = { version = "2.10.0", default-features = false, features = ["derive"], optional = true  }
+scale = { package = "parity-scale-codec", version = "3.6.1", default-features = false, features = [
+	"derive",
+	"max-encoded-len",
+], optional = true }
+
+[features]
+default = [ "scale" ]
+scale = [ "dep:scale", "scale-info" ]
+