Function step_attach_layer

UnitTests/UnitTest_AttachDetach/DemoKeeper.cpp:94–106

	}

	static void step_attach_layer()
	{
		MyGUI::Widget* widget = get_random(all_widgets);
		if (!widget)
			return;
		if (widget->isRootWidget())
		{
			std::string_view layername = get_layer();
			if (!layername.empty())
				MyGUI::LayerManager::getInstance().attachToLayerNode(layername, widget);
		}
		test_widgets();
	}

	static void step_attach_layer(int _count)
	{