Contracts: Stabilize XCM host fns (#4213)

See 
use-ink/ink#1912
use-ink/ink-docs#338

prdoc/pr_4213.prdoc

@@ -0,0 +1,11 @@
+title: "[pallet-contracts] stabilize xcm_send and xcm_execute"
+
+doc:
+  - audience: Runtime Dev
+    description: |
+     `xcm_send` and `xcm_execute` are currently marked as unstable. This PR stabilizes them.
+crates:
+- name: pallet-contracts
+  bump: major
+
+

substrate/frame/contracts/src/lib.rs

@@ -223,14 +223,14 @@ pub struct Environment<T: Config> {
 pub struct ApiVersion(u16);
 impl Default for ApiVersion {
 	fn default() -> Self {
-		Self(2)
+		Self(3)
 	}
 }
 
 #[test]
 fn api_version_is_up_to_date() {
 	assert_eq!(
-		109,
+		111,
 		crate::wasm::STABLE_API_COUNT,
 		"Stable API count has changed. Bump the returned value of ApiVersion::default() and update the test."
 	);

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

@@ -2104,7 +2104,6 @@ pub mod env {
 
 	/// Execute an XCM program locally, using the contract's address as the origin.
 	/// See [`pallet_contracts_uapi::HostFn::execute_xcm`].
-	#[unstable]
 	fn xcm_execute(
 		ctx: _,
 		memory: _,
@@ -2143,7 +2142,6 @@ pub mod env {
 
 	/// Send an XCM program from the contract to the specified destination.
 	/// See [`pallet_contracts_uapi::HostFn::send_xcm`].
-	#[unstable]
 	fn xcm_send(
 		ctx: _,
 		memory: _,