mayaUsdDuplicate verbose return

The command `cmds.mayaUsdDuplicate()` should return the path to the converted object. Also, with the `full` keyword argument to get the full path.

This is because if I already have an object in Maya called pCube1 and I duplicate a USD cube called pCube1, it will become pCube2.

Start by locating the implementation and tests for the `cmds.mayaUsdDuplicate()` command. Verify how duplicate names are resolved and how the `full` keyword should affect the returned path; done means the command returns the converted object's path in both modes, including when Maya renames a duplicate.

Written by the indexing model from the issue text.