After e3697710d0, if no UV map was found, then Cycles OSL would
generate UV coordinates for users. This was done to add UV coordinates
to lights, however it had the side effect of creating new UV
coordinates for other object types that don't have a UV map.
This lead to a rendering difference between OSL and SVM
when rendering meshes with no UV map, and objects with no
UV map, like curves.
This commit fixes this issue by adding a new "is_light" attribute to
Cycles OSL and using that to figure out if UV coordinates should be
generated for lights.
Pull Request: https://projects.blender.org/blender/blender/pulls/124673
e7ce8d33e3