Fix issue with MultiScaleVO and Single Pass Stereo

[bgolus]

Fixes an issue with MultiScaleVO showing incorrectly if XR and single pass stereo is enabled for a project, but the current camera not actually doing stereo rendering, like the scene view or when the HMD isn't active, or for "social" camera views.

[lukis101]

Updated the stereo check and variable name to match those in bloom effect