PVF: Remove artifact persistence across restarts (paritytech#2895)

Considering the complexity of
paritytech#2871 and the discussion
therein, as well as the further complexity introduced by the hardening
in paritytech#2742, as well as the
eventual replacement of wasmtime by PolkaVM, it seems best to remove
this persistence as it is creating more problems than it solves.

## Related

Closes paritytech#2863

substrate/utils/build-script-utils/src/version.rs

@@ -59,34 +59,3 @@ fn get_version(impl_commit: &str) -> String {
 		impl_commit
 	)
 }
-
-/// Generate `SUBSTRATE_WASMTIME_VERSION`
-pub fn generate_wasmtime_version() {
-	generate_dependency_version("wasmtime", "SUBSTRATE_WASMTIME_VERSION");
-}
-
-fn generate_dependency_version(dep: &str, env_var: &str) {
-	// we only care about the root
-	match std::process::Command::new("cargo")
-		.args(["tree", "--depth=0", "--locked", "--package", dep])
-		.output()
-	{
-		Ok(output) if output.status.success() => {
-			let version = String::from_utf8_lossy(&output.stdout);
-
-			// <DEP> vX.X.X
-			if let Some(ver) = version.strip_prefix(&format!("{} v", dep)) {
-				println!("cargo:rustc-env={}={}", env_var, ver);
-			} else {
-				println!("cargo:warning=Unexpected result {}", version);
-			}
-		},
-
-		// command errors out when it could not find the given dependency
-		// or when having multiple versions of it
-		Ok(output) =>
-			println!("cargo:warning=`cargo tree` {}", String::from_utf8_lossy(&output.stderr)),
-
-		Err(err) => println!("cargo:warning=Could not run `cargo tree`: {}", err),
-	}
-}