VideoBackends: add support to allow rendering to multiple output textures

Source/Core/VideoBackends/Metal/MTLGfx.h

@@ -28,7 +28,8 @@ public:
   std::unique_ptr<AbstractStagingTexture>
   CreateStagingTexture(StagingTextureType type, const TextureConfig& config) override;
   std::unique_ptr<AbstractFramebuffer>
-  CreateFramebuffer(AbstractTexture* color_attachment, AbstractTexture* depth_attachment) override;
+  CreateFramebuffer(AbstractTexture* color_attachment, AbstractTexture* depth_attachment,
+                    std::vector<AbstractTexture*> additional_color_attachments) override;
 
   std::unique_ptr<AbstractShader> CreateShaderFromSource(ShaderStage stage, std::string_view source,
                                                          std::string_view name) override;