gitadora: (arena model) single window mode + subscreen overlay (#486)

## Link to GitHub Issue, if one exists
#477 

## Description of change
This is a work in progress.

What works:
- [x] subscreen overlay shows the touch screen image (in windowed mode)
- [x] touch works in the overlay
- [x] only the main window is shown, other windows are not launched

What doesn't:
- [ ] game occasionally crashes when entering test menu?
- [ ] full screen mode is not tested at all due to monitor requirements
- [ ] need more polish (various options to control the behavior)

src/spice2x/launcher/options.h

@@ -100,8 +100,10 @@ namespace launcher {
             LoadGitaDoraModule,
             GitaDoraTwoChannelAudio,
             GitaDoraCabinetType,
+            GitaDoraArenaSingleWindow,
             GitaDoraLefty,
             GitaDoraWailHold,
+            GitaDoraSubOverlaySize,
             LoadJubeatModule,
             LoadReflecBeatModule,
             LoadShogikaiModule,