Exporting mayaUsdProxyShape node doesnt keep edits

**Describe the bug**
When we try to export a mayaUsdProxyShape as a Maya scene, it doesn't export the USD edits that was living in the Maya scene. This means any composition/edit made from that Stage node is not being exported (Anonymous layers, EditTarget, PrimSpec/AttrSpec, new defs, etc).


**Steps to reproduce**
At its simplest way to reproduce the issue:
1. Create Stage with New Layer
2. Create a sphere Prim
3. Select mayaUsdProxyShape node
4. File -> Export Selection -> .ma

**Expected behavior**
Any USD Data that would normally be saved within the Maya scene should also be exported (Anonymous layers, EditTarget's Prim/AttrSpec, etc). The Export should act exactly like the "Save all edits (including USD) to the Maya scene file".

**Specs:**
- Alma Linux 9.4
- Maya 2024
- mayaUsd 0.30 & 0.31

**Additional Info**:
- Our Save USD Options is set to "Save all edits (including USD) to the Maya scene file"