Fix GLSL type in LightCompoundData node

[tdavidovicNV]

In prep for the Slang merge, I was looking how close are the remaining Nodes between GenMsl and GenGlsl. And I found that the GenGlsl one was using float3 type instead of the vec3. I don't believe there is any alias for that, and even if there was, I think using the native type is the better idea. Also, it seems like there is no test coverage for this node, as I was running it with full tests (modified the _options to just point to resources/Materials) and this didn't come up.

[ld-kerley]

This looks like it might have been a copy/paste bug I introduced - thanks for catching it.

You do raise a great question though - I wonder what the right way to get test coverage added for this code path is. @jstone-lucasfilm - do you have any insights there?

[jstone-lucasfilm]

Great catch, thanks @tdavidovicNV!

@ld-kerley Based on Tomas's description above, it sounds as if we don't yet have an example in our test suite that leverages this specific code path. Assuming we can express one through a new or extended MTLX file in our test suite, that sounds like the best path forward.

[ld-kerley]

Its always been a little unclear to me how the lights in MaterialX are intended to be used - so I was more asking if you have any concrete examples we can add - or have any insight as to how the lights are intended to be used, that would help me be able to construct some unit tests.