Hydra: Material graph changes invalidate bound GPrims

[dgovil]

Description of Issue

We are seeing that when a material has its graph topology changed, it causes Hydra to invalidate the material AND all gprims that have the material bound to it. This calls into the render delegates Create and Destroy method for each of the prims.

This feels somewhat costly for persisting the scene graph itself as artists iterate on shader looked.

System Information (OS, Hardware)

• macOS 15.1

Package Versions

• USD 24.3 and 24.5 . Our team hasn't updated to 24.11 but I didn't see any code changes that stood out to me regarding it
• Attempted with and without USDIMAGINGGL_ENGINE_ENABLE_SCENE_INDEX

[jesschimein]

Filed as internal issue #USD-10414