iidx,sdvx: disable subscreen overlay if -monitor is in use (#471)

## Link to GitHub Issue, if one exists
#345 

## Description of change
If TDJ / VM mode is active AND user is enabled `-monitor` option (and
the value isn't 0, the primary monitor)

then disable the subscreen overlay, show an error message instead.

We're doing this because both games cannot accept emulated touch input
if `-monitor` option is in use. There is not much point in displaying
the second screen's image, other than to REALLY confuse people when
nothing happens when they click on it.

## Testing
Tested both games with `-monitor`.

src/spice2x/launcher/options.cpp

@@ -207,7 +207,7 @@ static const std::vector<OptionDefinition> OPTION_DEFINITIONS = {
         .name = "monitor",
         .desc = "Sets the display that the game will be opened in, for multiple monitors.\n\n"
             "0 is the primary monitor, 1 is the second monitor, and so on.\n\n"
-            "Not all games will respect this. Does not work at all with multi-monitor games like TDJ/UFC. "
+            "Not all games will respect this. Not recommended for multi-monitor games like Lightning Model / Valkyrie Model modes. "
             "Disable Full Screen Optimizations for best results",
         .type = OptionType::Integer,
         .category = "Graphics (Full Screen)",