Native ID2D1RenderTarget::SaveDrawingState method stores in ID2D1DrawingStateBlock only transform, antialiasing mode, text-rendering options and tags but not currently set ID2D1Layers (which are used in wxD2DContext for clipping purposes). Therefore current stack of layers has to be stored "manually" alongside ID2D1DrawingStateBlock in a dedicated data structure (LayerData) in PushState() and restored also "manually" in PopState().
Closes#17626.