Fix the restart-into-a-screen arguments, broken by the cmdline refactor

Centralizing command line parsing replaced the hand-rolled --gamesettings and
--touchscreentest argv checks in NativeInit with a single --start-screen=<name>
option, and made an unrecognized "--" argument a hard parse error. The two
System_RestartApp callers still passed the old flags.

So changing the graphics backend killed PPSSPP for good: the new process starts,
fails to parse --gamesettings, and returns 1 from WinMain before a window ever
exists. The error goes to stderr, which nobody sees in a GUI build, so it just
looks like the app quit instead of restarting.

Restarts that pass no arguments (the memstick screen, and the edit-then-restore
path) were unaffected, since an empty argument string makes ExitAndRestart reuse
the original command line.

Also move the TouchTestScreen push inside the touchscreentest branch - it looks
like a brace that didn't move during the refactor, and it would otherwise push a
touch test screen for every --start-screen value.

UI/NativeApp.cpp

@@ -807,8 +807,8 @@ void NativeInit(int argc, const char *argv[], const CommandLineOptions &cmdLineO
 		// Launch into specified start screen. This is useful for testing UI, more screens can be easily added here.
 		if (equals(cmdLineOptions.startScreen.value(), "touchscreentest")) {
 			g_screenManager->switchScreen(new MainScreen());
+			g_screenManager->push(new TouchTestScreen(Path()));
 		}
-		g_screenManager->push(new TouchTestScreen(Path()));
 		if (equals(cmdLineOptions.startScreen.value(), "gamesettings")) {
 			g_screenManager->switchScreen(new LogoScreen(AfterLogoScreen::TO_GAME_SETTINGS));
 		} else if (equals(cmdLineOptions.startScreen.value(), "developertools")) {