gitadora: add native dual fullscreen for Arena (#846)

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

Fixed https://github.com/spice2x/spice2x.github.io/issues/740

## Description of change

- Enable native D3D9 adapter-group dual fullscreen for the GITADORA
Arena model when the two-screen MAIN + SMALL configuration is selected
without windowed mode.
- Present MAIN and SMALL on their respective monitor heads while keeping
the invisible LEFT and RIGHT targets offscreen.
- Scope the new fake-swap-chain query behavior to the hidden GITADORA
two-head targets, preserving existing behavior for other games and
configurations.

The existing borderless-windowed two-screen path could not consistently
keep input and game timing synchronized and also reduced rendering
performance. Native dual fullscreen avoids that windowed composition
path.

## Testing

- Manually tested GITADORA Arena with separate MAIN and SMALL monitors
in fullscreen mode. Windowed mode still works if the user chooses to use
that.
- Confirmed both displays render correctly, touch input works on the
SMALL screen, gameplay input stays synchronized, and gameplay holds a
steady 60 FPS.
- Built `spicetools_spice64` at commit `e4a98e9` with the repository
Docker toolchain.
- Confirmed no new compiler warnings.
- Confirmed the forbidden static DLL import check passes.
- Confirmed the Windows 7 DLL compatibility check reports `All DLLs
OK!`.

---------

Co-authored-by: vgod <428979+vgod@users.noreply.github.com>

src/spice2x/hooks/graphics/backends/d3d9/d3d9_backend.h

@@ -2,6 +2,8 @@
 
 #include <d3d9.h>
 
+#include "d3d9_gfdm.h"
+
 // {EEE9CCF6-53D6-4326-9AE5-60921B3DB394}
 static const GUID IID_WrappedIDirect3D9 = {
     0xeee9ccf6, 0x53d6, 0x4326, { 0x9a, 0xe5, 0x60, 0x92, 0x1b, 0x3d, 0xb3, 0x94 }