GPU: Implement non-interleaved interlaced rendering

Fixes screen shaking in True Pinball.

src/core/gpu_hw.h

@@ -27,6 +27,13 @@ public:
     OnlyTransparent
   };
 
+  enum class InterlacedRenderMode : u8
+  {
+    None,
+    InterleavedFields,
+    SeparateFields
+  };
+
   GPU_HW();
   virtual ~GPU_HW();
 
@@ -189,6 +196,20 @@ protected:
     return m_batch.check_mask_before_draw || m_render_api != HostDisplay::RenderAPI::D3D11;
   }
 
+  /// Returns the interlaced mode to use when scanning out/displaying.
+  ALWAYS_INLINE InterlacedRenderMode GetInterlacedRenderMode() const
+  {
+    if (IsInterlacedDisplayEnabled())
+    {
+      return m_GPUSTAT.vertical_resolution ? InterlacedRenderMode::InterleavedFields :
+                                             InterlacedRenderMode::SeparateFields;
+    }
+    else
+    {
+      return InterlacedRenderMode::None;
+    }
+  }
+
   void FillVRAM(u32 x, u32 y, u32 width, u32 height, u32 color) override;
   void UpdateVRAM(u32 x, u32 y, u32 width, u32 height, const void* data) override;
   void CopyVRAM(u32 src_x, u32 src_y, u32 dst_x, u32 dst_y, u32 width, u32 height) override;