USDZExporter: Support metalness/roughness factor and Image combination

[optimus007]

Is your feature request related to a problem? Please describe.
Currently in usdzExporter , the roughnessMap and metalnessMap is only exported if roughness is 1 and metalness 1. #22201
this was due to the limitation that usdz generated does not have support for both a factor and image .

A clear and concise description of what the problem is.
On a metal ring model I exported which had roughness of 0.75 and a dark roughness map , due to the conditions above the image was skipped and the model was exported with just float inputs:roughness = 0.75 which made the usdz model very rough and inconsistent with the three js render

Describe the solution you'd like
Since there have been some good updates from @sunag and @yuta-hayashi ,I was wondering if we can revisit this topic and implement a alternate solution

fiddle to Test

[sunag]

I was looking for references but only found this one based on NodeGraph:
Do you know some other reference too?

https://github.com/PixarAnimationStudios/USD/blob/dev/pxr/usd/usdMtlx/testenv/testUsdMtlxFileFormat.testenv/baseline/NodeGraphs.usda

[optimus007]

something from here might come in handy
https://github.com/google/usd_from_gltf/blob/master/convert/materializer.cc

from usd_from_gltf

[sdarpeng]

I think this is a good issue too.

[elalish]

Possibly related: this example when loading AR on an iPhone uses USDZExporter to create the file for Quick Look, but we get the message "Object requires a newer version of iOS", which is Apple's lovely message meaning something went wrong parsing the USDZ. In this case, the object has a factor but no texture at all. Does anyone know if there's a way to support that in USDZ? @mrdoob @grorg.

[optimus007]

@elalish The case of zero textures and just factors like roughness:0.1 and metalness:1 should export correctly , like you said that error message can be caused due to wide variety of reasons (one silly case i remember is presence of symbols in the material names )

Made a fiddle please test it out, (the usdz file can renamed to .zip and can be opened on any os and the materials info can be checked)

[Mirei3D]

This seems to be fixed by #29216