graphics: option to include subscreens in screenshot (#866)

## Link to GitHub Issue or related Pull Request, if one exists
#0

## Description of change
Adds `-screenshotsub`. Off by default. When on, screenshots include the
subscreens. All subscreens are captured, even if they are hidden from
view. Works for all four screens of gitadora arena model as well.

This should also fix an issue with API / companion app not capturing
gitadora subscreen correctly.

Note: only done for DX9... DX11 will need another PR to make this work.

Unrelated to this PR, there seems to be a bug with gitadora not
accepting mouse or api touch input.

## Testing

src/spice2x/hooks/graphics/graphics.h

@@ -112,6 +112,7 @@ extern bool FAKE_SUBSCREEN_ADAPTER;
 extern std::string GRAPHICS_DEVICEID;
 extern std::string GRAPHICS_SCREENSHOT_DIR;
 extern bool GRAPHICS_SCREENSHOT_INCLUDE_OVERLAY;
+extern bool GRAPHICS_SCREENSHOT_SUBSCREENS;
 
 // Direct3D 9 settings
 extern std::optional<UINT> D3D9_ADAPTER;
@@ -146,7 +147,8 @@ bool graphics_capture_receive_jpeg(int screen, TooJpeg::WRITE_ONE_BYTE receiver,
         bool rgb = true, int quality = 80, bool downsample = true, int divide = 0,
         uint64_t *timestamp = nullptr,
         int *width = nullptr, int *height = nullptr);
-std::string graphics_screenshot_genpath();
+// the returned path is for screen 0; any extra screens only reserve their suffixed names
+std::string graphics_screenshot_genpath(const std::vector<int> &screens = {});
 
 // graphics_windowed.cpp
 void graphics_windowed_wndproc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);