Indexed AbcGeomArb are not imported/created

[BSalem]

if an alembic has indexed GeomArbitrary variable like colorSet for example has been loaded using UsdIn, the indexed variable won't be created in katana, the issue behind this is that UsdGeomPrimvarsAPI::GetPrimvars() won't return the primvar because in case of such indexed variables, the primvar name is formed incorrectly:
it will be primvars:colorSet:vals, primvars:colorSet:indices other than primvars:colorSet and primvars:colorSet:indices

due to the above difference, UsdGeomPrimvarsAPI::GetPrimvars() doesn't respect/recognize the colorSet as primvar, so it's not returned, and accordingly, not created in katana (since usdAbc calls this function to convert all geomArb to primvars)

I fixed this issue in the following USD PR, but not able to do pull request on Fonudry USD, as well as that I'm not able to even test it because KatanaUsd Plugin fails to compile with -DUSD_ROOT other than the foundry's patched one:

PixarAnimationStudios/OpenUSD#1635