gitadora: show LEFT / RIGHT screens on sub screen in landscape mode (#900)

## Link to GitHub Issue or related Pull Request, if one exists
Continues #899 

## Description of change
#899 added the ability to display the gitadora subscreen in lanscape
mode with black bars on the side. With the new option the black bars can
instead display the LEFT / RIGHT screens, completing the two-monitor
full screen use case for arena model.

## Testing

src/spice2x/launcher/options.cpp

@@ -1330,6 +1330,25 @@ static const std::vector<OptionDefinition> OPTION_DEFINITIONS = {
         },
         .quick_setting_category = "Game",
     },
+    {
+        // GitaDoraArenaSubLayout
+        .title = "GitaDora Arena Subscreen Layout (EXPERIMENTAL)",
+        .name = "gdasublayout",
+        .desc = "For Arena Model full screen two-window mode: select the image layout on the second monitor.\n\n"
+            "portrait (default): default subscreen @ 800x1280\n\n"
+            "landscape: pillarboxed subscreen @ 1920x1080\n\n"
+            "combine: LEFT + SMALL + RIGHT screens side by side @ 1920x1080\n\n"
+            "For landscape and combine, -forceressub can be used to override the resolution.",
+        .type = OptionType::Enum,
+        .game_name = "GitaDora",
+        .category = "Game Options",
+        .elements = {
+            {"portrait", ""},
+            {"landscape", ""},
+            {"combine", ""}
+        },
+        .quick_setting_category = "Game",
+    },
     {
         // GitaDoraArenaAsioDriver
         .title = "GitaDora Arena ASIO driver",
@@ -3425,19 +3444,6 @@ static const std::vector<OptionDefinition> OPTION_DEFINITIONS = {
         .type = OptionType::Bool,
         .category = "General Overlay",
     },
-    {
-        // GitaDoraSubscreenLandscape
-        .title = "GitaDora Arena Landscape Subscreen (EXPERIMENTAL)",
-        .name = "gdsublandscape",
-        .desc = "For Arena Model full screen two-window mode: drive the SMALL touch subscreen "
-            "with a landscape monitor instead of a portrait one.\n\n"
-            "The portrait image is centered and black bars fill the space on either side.\n\n"
-            "Launches at 1920x1080; use -forceressub if you need a different resolution.",
-        .type = OptionType::Bool,
-        .game_name = "GitaDora",
-        .category = "Game Options",
-        .quick_setting_category = "Game",
-    },
 };
 
 const std::vector<std::string> &launcher::get_categories(Options::OptionsCategory category) {