SceneModel as reusable render state for GUI samples in WinForms, WPF, etc

[IngmarBitter]

[IDEA] refactor WinForms sample when we have a WPF or other GUI sample such that in the UI library specific code is minimal code. All the Dx12 rendering setup should be in a separate scene model that is keeping the render configuration state. The GUI just provides a way to update that state. This will maximize the code reuse between the different GUI library samples.