Contracts Bump ApiVersion and add test (#3619)

ApiVersion should have been bumped with
https://github.com/paritytech/polkadot-sdk/pull/3606
this does that and add a test so we don't forget to do that everytime

substrate/frame/contracts/src/wasm/mod.rs

@@ -21,6 +21,9 @@
 mod prepare;
 mod runtime;
 
+#[cfg(test)]
+pub use runtime::STABLE_API_COUNT;
+
 #[cfg(doc)]
 pub use crate::wasm::runtime::api_doc;