GLB import should support all glTF extensions the engine supports

[mvaligursky]

• ideally when we import glb file that uses extensions the engine (and the Editor) supports, the imported glb version should preserve those extensions, materials should be correctly configured etc ..

I have not investigated which extensions are supported, but recently added KHR_materials_anisotropy is not supported, when we import models using it (from engine examples), the anisotropy is not configured.

[Maksims]

This also is useful if users have custom extensions/data, and want to manually engage with data using ContainerHandler.

[mvaligursky]

another related tickets

• https://github.com/playcanvas/editor/issues/1225
• https://github.com/playcanvas/editor/issues/1000

[willeastcott]

Also related to: https://github.com/playcanvas/editor/issues/1308