As suggested by @Vanuan. and already implemented in new experimental BIM Wall: 1084a4b0a9
Draft: updated Draft Edit
thanks to the suggestions by @Vanuan
Draft: further bugfixing and improvements in Draft_Edit
Draft: moved Draft_Edit preview code into respective GuiTools
Because Gui::ViewProviderLink can be used to override the view provider
of any object, it is not safe to assume view provider type without
explicit checking.
Small fixes where the `get_svg` function is used, for example,
in the (obsolete) `DrawingView` class and `Arch_SectionPlane`.
Also update the unit tests accordingly.