gitadora: (arena model) booting fullscreen with one monitor (#696)

## Link to GitHub Issue or related Pull Request, if one exists
#477 

## Description of change
By default the game needs 4 monitors.

With the new option to disable subscreens, you can now boot fullscreen
with a single 4K monitor, with subscreen overlay enabled. Side monitors
are not shown in the overlay; only the touch screen is emulated.

## Future work

- [ ] custom resolution (-forceres) doesn't work properly (hooking
ResetEx does allow the game to boot but will render incorrectly;
probably needs hex edits)
- [x] enable this automatically if the user has fewer than 4 monitors
- [ ] ability to boot with a 4k main screen + small subscreen (with no
side screens which do nothing gameplay wise), but this whole display
emulation is a nightmare to work with & test thoroughly so it'll have to
be in the future.


## Testing
Checklist:

- [x] fs on 1 monitor with option set
- [x] fs on 2 monitor with option set
- [x] windowed - default (4 windows, no overlay)
- [x] windowed - with option set (1 window, overlay)
- [x] fs with 4 monitors?
- [x] check popn hc for regression

src/spice2x/hooks/graphics/graphics.cpp

@@ -421,7 +421,7 @@ static HWND WINAPI CreateWindowExA_hook(DWORD dwExStyle, LPCSTR lpClassName, LPC
     }
 
     // only hook touch window if multiple windows are allowed
-    if (is_gfdm_sub_window && !games::gitadora::ARENA_SINGLE_WINDOW) {
+    if (is_gfdm_sub_window && GRAPHICS_WINDOWED && !GRAPHICS_PREVENT_SECONDARY_WINDOW) {
         GFDM_SUBSCREEN_WINDOW = result;
         graphics_hook_subscreen_window(GFDM_SUBSCREEN_WINDOW);
     }
@@ -702,7 +702,7 @@ static BOOL WINAPI SetWindowPos_hook(HWND hWnd, HWND hWndInsertAfter,
 
 static BOOL WINAPI ShowWindow_hook(HWND hWnd, int nCmdShow) {
     if (games::gitadora::is_arena_model() &&
-        games::gitadora::ARENA_SINGLE_WINDOW &&
+        GRAPHICS_PREVENT_SECONDARY_WINDOW &&
         hWnd != GRAPHICS_HOOKED_WINDOW) {
         log_info("graphics", "ShowWindow_hook - hiding sub window {}", fmt::ptr(hWnd));
         return true;