UI Builder Material properties can be added multiple times redundantly when using the Material Definition foldout

Steps to reproduce:

1. Create a new project using Universal 3D template
2. Go to Assets > Create > Shader Graph > URP > UI Shader Graph and open it
3. In the Blackboard, click "+" and add "Color" 
4. Save and exit
5. Create a new UXML Document and open it in UI Builder
6. Add a Visual Element to the Hierarchy
7. In the Inspector, expand the Material foldout and assign the newly created Material from Shader Graph
8. Click on the "+" button and select "Color"
9. Repeat 8th step
10. Observe the behavior

Actual results: The exact same property can be added an infinite amount of times. Modifying a duplicated property's value instantly resets it to the top property's value making other properties redundant

Expected results: Properties that have already been added to the Material Definition override list are hidden, disabled, or grayed out in the "+" dropdown menu

Reproducible with versions: 6000.3.12f1, 6000.4.1f1, 6000.5.0b2, 6000.6.0a2

Can’t test with versions: 6000.0.71f1 (Materials foldout not available)

Tested on (OS): Windows 11

Notes:

• This applies to all property types exposed in the Shader Graph blackboard