Feature/bifrost 10105/add support for usd type name maya attribute

[frenchdog]

When importing a Maya Model in a Bifrost USD graph, if a Maya attribute named "USD_typeName" is present on the DAG node, it will be used to set the prim type in the imported selection.

(such USD_typeName attribute is used by the Maya USD exporter to create USD prim with types who don't exist in Maya, so we use the same attribute).

The second commit is not related to this ticket. Just a renaming to improve readability.