Add an option to present/skip presenting duplicate frames

Currently, we do not display every second frame in 25fps/30fps games
which run to vsync. This improves performance as there's less rendering
for the GPU to perform, but when combined with vsync, could cause frame
pacing issues.

This commit adds an option to force every frame generated by the console
to be displayed to the host, which may improve pacing for these games.

Source/Core/Core/Config/GraphicsSettings.cpp

@@ -154,6 +154,8 @@ const ConfigInfo<bool> GFX_HACK_DISABLE_COPY_TO_VRAM{{System::GFX, "Hacks", "Dis
                                                      false};
 const ConfigInfo<bool> GFX_HACK_DEFER_EFB_COPIES{{System::GFX, "Hacks", "DeferEFBCopies"}, true};
 const ConfigInfo<bool> GFX_HACK_IMMEDIATE_XFB{{System::GFX, "Hacks", "ImmediateXFBEnable"}, false};
+const ConfigInfo<bool> GFX_HACK_SKIP_DUPLICATE_XFBS{{System::GFX, "Hacks", "SkipDuplicateXFBs"},
+                                                    true};
 const ConfigInfo<bool> GFX_HACK_COPY_EFB_SCALED{{System::GFX, "Hacks", "EFBScaledCopy"}, true};
 const ConfigInfo<bool> GFX_HACK_EFB_EMULATE_FORMAT_CHANGES{
     {System::GFX, "Hacks", "EFBEmulateFormatChanges"}, false};

Source/Core/Core/Config/GraphicsSettings.h

@@ -111,6 +111,7 @@ extern const ConfigInfo<bool> GFX_HACK_SKIP_XFB_COPY_TO_RAM;
 extern const ConfigInfo<bool> GFX_HACK_DISABLE_COPY_TO_VRAM;
 extern const ConfigInfo<bool> GFX_HACK_DEFER_EFB_COPIES;
 extern const ConfigInfo<bool> GFX_HACK_IMMEDIATE_XFB;
+extern const ConfigInfo<bool> GFX_HACK_SKIP_DUPLICATE_XFBS;
 extern const ConfigInfo<bool> GFX_HACK_COPY_EFB_SCALED;
 extern const ConfigInfo<bool> GFX_HACK_EFB_EMULATE_FORMAT_CHANGES;
 extern const ConfigInfo<bool> GFX_HACK_VERTEX_ROUDING;