Improve CodeExecutor (#2358)

Since `sp-state-machine` and `GenesisConfigBuilderRuntimeCaller` always
set `use_native` to be false.
We should remove this param and make `NativeElseWasmExecutor` behave
like its name.
It could make the above components use the correct execution strategy.

Maybe polkadot do not need about `NativeElseWasmExecutor` anymore. But
it is still needed by other chains and it's useful for debugging.

---------

Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: command-bot <>
Co-authored-by: Michal Kucharczyk <1728078+michalkucharczyk@users.noreply.github.com>

substrate/primitives/state-machine/src/lib.rs

@@ -289,7 +289,7 @@ mod execution {
 
 			let result = self
 				.exec
-				.call(&mut ext, self.runtime_code, self.method, self.call_data, false, self.context)
+				.call(&mut ext, self.runtime_code, self.method, self.call_data, self.context)
 				.0;
 
 			self.overlay
@@ -1120,10 +1120,9 @@ mod tests {
 			_: &RuntimeCode,
 			_method: &str,
 			_data: &[u8],
-			use_native: bool,
 			_: CallContext,
 		) -> (CallResult<Self::Error>, bool) {
-			let using_native = use_native && self.native_available;
+			let using_native = self.native_available;
 			match (using_native, self.native_succeeds, self.fallback_succeeds) {
 				(true, true, _) | (false, _, true) => (
 					Ok(vec![