Graphics: Rework RenderTargets

- RenderTarget have been moved to the Graphics module and are now lightweight objects between the target of rendering (swapchain or texture)
- RenderTexture no longer require a blit between the framegraph texture and the target texture (the target texture is now directly rendered onto using a new feature of the framegraph)
- ForwardFramePipeline viewers are now properly ordered by render order

examples/WidgetDemo/main.cpp

@@ -105,7 +105,7 @@ int main(int argc, char* argv[])
 	{
 		viewer2D.emplace<Nz::NodeComponent>();
 
-		auto& cameraComponent = viewer2D.emplace<Nz::CameraComponent>(&windowSwapchain, Nz::ProjectionType::Orthographic);
+		auto& cameraComponent = viewer2D.emplace<Nz::CameraComponent>(std::make_shared<Nz::RenderWindow>(windowSwapchain), Nz::ProjectionType::Orthographic);
 		cameraComponent.UpdateClearColor(Nz::Color(0.46f, 0.48f, 0.84f, 1.f));
 	}