Duplicate Shape Node on Import

**Describe the bug**
Upon importing a .usd file that contains a structure of:
+ asset_name
+ geo
+ pCone1 (Xform or transform node)
+ pCone1Shape (Mesh or shape node)

the imported hierarchy appears as:
+ asset_name
+ geo
+ pCone1 (Xform or group)
+pCone1Shape (Xform or transform node)
+ pConeShape1Shape (Mesh or shape node)

this is when exporting you do NOT enable 'Merge Transform and Shape Nodes' which in our case (and the case of blender usd export for example) does not do.

**Steps to reproduce**
1. Create the structure above using groups and a pCone1
2. Select hierarchy and go File > Export Selection, do NOT enable 'Merge Transform and Shape Nodes'.
3. File > Import your .usd file

**Expected behavior**
I think the usd importer may require the inverse option of the exporters 'Merge Transform and Shape Nodes'. Allowing it to know that the `def Mesh "pConeShape1"` should just become the shape node for the `def Xform "pCone1"` above.

**Attachments**

**Specs (if applicable):**
- Windows-10-10.0.19045-SP0 64 Bits
- Maya 2025
- mayaUsdPlugin: 0.27.0