PixarAnimationStudios/OpenUSD

AI Summary: The task requires modifying the usdAbc library to correctly handle uint-indexed primvars written by Maya's Alembic plugin. Specifically, the change should ensure that additional UV sets (with uint indices) are treated as indexed primvars, converting them to the appropriate format (similar to how primary UV sets are handled) to be correctly read by USD and downstream renderers like Arnold. This involves leveraging the Alembic API's `isUV()` function to identify additional UV sets.