Import materialx as a godot material shader

[fire]

Describe the project you are working on:

Describe the problem or limitation you are having in your project:

Describe the feature / enhancement and how it helps to overcome the problem or limitation:

Describe how your proposal will work, with code, pseudocode, mockups, and/or diagrams:

If this enhancement will not be used often, can it be worked around with a few lines of script?:

Is there a reason why this should be core and not an add-on in the asset library?:

[fire]

Duplicate.

[Calinou]

Superseded by #714.