Please allow easy highlighting of geomsubsets in hydra clients

[koen-v]

As discussed in this thread on the OpenUsd forum:
https://forum.aousd.org/t/tips-for-working-with-geomsubsets/1959/3

Geomsubsets are a great way to retain enough flexibility to assign materials to large polygin soups ( which many tools prefer over large numbers of tiny UsdGeom prims. However currently, there are very few options to explore and debug the subsets. Enabling an easy way to highlight membership in a 3d viewport would go a long way towards making this easier.

Thanks,
Koen

[jesschimein]

Filed as internal issue #USD-10389