Use QVTKOpenGLNativeWidget instead of QVTKOpenGLStereoWidget, except when --stereo is passed
Since the QVTKOpenGLStereoWidget seems to break more often than expected and to have a few issue (#19364 (closed)), we may want to use QVTKOpenGLNativeWidget by default unless stereo is actively needed.
Edited by Mathieu Westphal (Kitware)