gitadora: allow a landscape monitor to display subscreen (#899)

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

## Description of change
Arena Model's SMALL touch subscreen is a portrait (800x1280) panel -
however, it's common for people to set up a touch screen in landscape
orientation since IIDX/SDVX/popn all use landscape.

Add a new option, `-gdsublandscape`, which forces the subscreen to
launch at 1080p landscape. The image is rendered with black bars on the
sides. Touches will be unaligned initially; user needs to go into test
mode and recalibrate. In reality this option is just a short hand for
`-forceressub 1920,1080`.

Wire up `-forceressub` which previously didn't work for gitadora, so
that a resolution other than 1080p can be used in either orientation. In
other games `-forceressub` just forces the rendering resolution and
IIDX/SDVX/popn's game engine automatically stretches to fill... however
for gitadora it works differently since we want to keep the aspect ratio
of the original screen; it instead hijacks the back buffer and makes the
game draw to an intermediate buffer.

## Testing

src/spice2x/hooks/graphics/backends/d3d9/d3d9_device.h

@@ -11,6 +11,7 @@
 #include "util/logging.h"
 
 #include "d3d9_fake_swapchain.h"
+#include "d3d9_gfdm.h"
 #include "d3d9_swapchain.h"
 
 /*
@@ -279,6 +280,7 @@ struct WrappedIDirect3DDevice9 : IDirect3DDevice9Ex {
     std::array<D3DPRESENT_PARAMETERS, 4> gfdm_logical_group_parameters {};
     bool gfdm_logical_group_parameters_valid = false;
     IDirect3D9 *gfdm_parent_d3d = nullptr;
+    GfdmSmallHead gfdm_small_head;
 
     std::mutex gfdm_recovery_mutex;
     std::array<D3DPRESENT_PARAMETERS, 2> gfdm_recovery_parameters {};