Add guard to zSpace-related render windows

zSpace render windows are dedicated to stereo rendering on zSpace Inspire hardware. We expect to use them with StereoRender enabled. If not, they will display nothing. But we need to add a check to prevent the SubmitFrame method to be called in that case. This method (zSpace API) can crash on some circumstances (for example when going full screen) when StereoRender is not enabled. In the future, further investigations could be done to handle such case in a better way.

Also increase a bit the default stylus ray width to reduce aliasing impact on it.