[MAYA-112143] Ability to edit reference paths within a USD stage

When using a USD stage with a reference to a given USD file, it would be great if there was a way to edit the reference file path and also to specify a specific prim to reference.

For example in this setup below, the `Def1` prim references the Stratocaster USD. However I cannot change the file path after referencing (only able to clear or add a new one), nor can I specify an explicit prim within that file to reference. e.g. if i only wanted to reference in the guitar body, and not the stand, i could not.


Ideally it would be possible to change the reference paths and specify specific prim paths like in the mayaUsdProxy node's Attribute Editor.