USD Layer Editor - List layer Edits

**Is your feature request related to a problem? Please describe.**
When using the USD Layer editor, we miss the ability to undo some of the edits in a dirty layer. we might not want to delete all edits and redo the work we really want to keep.

example:
if someone is making edits inside a layer, layout.usd, they might edit multiple prims in multiple ways. to keep it simple let's say we change two prim's transform. cube and sphere.
The layer will get dirty and if I save I will save both edits. But I might want to undo the cube xform edit to only save the sphere edits.

Right now, I believe the only way to do this is to either revert layer to file, losing both edits and having to redo sphere xform edit.
Or save both edits and then open the layout.usd in a text editor and remove the edits we don't want to keep.

**Describe the solution you'd like**
I would suggest adding a new button when right-clicking on a layer from the USD layer editor. This button will work similarly to the List Reference Edits window from the reference editor.

Maybe I'm missing something and there is a way to do this. If not maybe there is a better way to handle this problem.
Thanks