USD Layer Editor should allow for layer renaming

As our artists are starting to use the UFE workflows, a common request has been the desire to rename layers after they've been created. If they make a mistake during the naming process they need to go manually chase down everything at this time to reflow it.

If the layer editor could have the ability to rename layers, it would allow for artists to more easily change things like they would with any other file based workflow.

Start by locating the USD Layer Editor and the UFE workflow used when layers are created. Trace how an existing layer name is represented and changed, then verify that renaming works for an already-created layer without requiring artists to manually reflow related work.

Written by the indexing model from the issue text.