Tileset rendering does not work correctly with a Dynamic Material Instance

[kring]

Reported here:
https://community.cesium.com/t/cesium-for-unreal-3dtiles-dynamicmaterial/37034

To reproduce, create a Level Blueprint like this:
https://blueprintue.com/blueprint/oyczy--l/

Click Play-in-Editor, and the tileset will render, but it will be missing its raster overlays (among other things).

The reason is that the new material doesn't have UCesiumMaterialUserData attached to it, so it doesn't know the mapping between material layer name (such as Overlay0) and the material layer index used to set material parameters. Adding UCesiumMaterialUserData is not an option, because the API necessary to find the layer names is only available in the Editor.

The best solution, I think, is to modify the code starting here:
https://github.com/CesiumGS/cesium-unreal/blob/v2.11.0/Source/CesiumRuntime/Private/CesiumGltfComponent.cpp#L3024
So that, rather than just checking the pBaseAsMaterialInstance for UCesiumMaterialUserData, it also walks the Parent chain looking for a parent material that has it.