Investigate usd generative procedural node

[cpichard]

Describe the feature you'd like We would like to have a better understanding of how generative procedural are passed and interpreted by arnold-usd and arnold

https://graphics.pixar.com/usd/dev/api/class_usd_proc_generative_procedural.html

[autodesk-oss-arnold-bot[bot]]

Issue synced internally to ARNOLD-13315