D3D: Fix EFB depth buffer copies, filtering on scaled EFB copies when MSAA is enabled, real XFB filtering

Since ResolveSubresource cannot be used with depth textures (and throws an error with the debug layer enabled), use a shader which selects the minimum depth value from all samples.

Changes the sampler by XFBEncoder to use a linear filter, rather than point, to match GL behavior.

Source/Core/VideoBackends/D3D/FramebufferManager.h

@@ -104,6 +104,7 @@ private:
 
 	static unsigned int m_target_width;
 	static unsigned int m_target_height;
+	static ID3D11DepthStencilState* m_depth_resolve_depth_state;
 };
 
 }  // namespace DX11