executor: Move runtime version caching out of WasmRuntime interface. (#3993)

* executor: Move runtime caching out of WasmRuntime interface.

The runtime version is now fetched and cached at a higher level, not
within the WasmRuntime trait implementations.

* executor: Require successful querying of runtime version.

substrate/core/executor/src/lib.rs

@@ -73,7 +73,6 @@ pub fn call_in_wasm<E: Externalities>(
 	heap_pages: u64,
 ) -> error::Result<Vec<u8>> {
 	let mut instance = wasm_runtime::create_wasm_runtime_with_code(
-		ext,
 		execution_method,
 		heap_pages,
 		code,