Fix screenshot dimensions when at 1x scale

This was regressed by ART.
Prior to ART, the screenshots were saved at the title's framebuffer resolution. A misunderstanding of the existing logic led to screenshot dimensions becoming dependent on the host render window size.

This changes the behavior to match how it was prior to ART at 1x, with screenshots now always being the title's framebuffer dimensions scaled by the resolution scaling factor.

src/core/frontend/framebuffer_layout.cpp

@@ -25,7 +25,12 @@ FramebufferLayout DefaultFrameLayout(u32 width, u32 height) {
     ASSERT(height > 0);
     // The drawing code needs at least somewhat valid values for both screens
     // so just calculate them both even if the other isn't showing.
-    FramebufferLayout res{width, height, false, {}};
+    FramebufferLayout res{
+        .width = width,
+        .height = height,
+        .screen = {},
+        .is_srgb = false,
+    };
 
     const float window_aspect_ratio = static_cast<float>(height) / static_cast<float>(width);
     const float emulation_aspect_ratio = EmulationAspectRatio(