Implement new GLTF loader and saver

[mrhegemon]

Rebuild all current scenes

Add MSFT_lod support to the GLTF loader and pipeline https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Vendor/MSFT_lod

https://github.com/takahirox/three-gltf-extensions https://github.com/takahirox/three-gltf-extensions/blob/main/loaders/MSFT_lod/MSFT_lod.js

[mrhegemon]

https://github.com/KhronosGroup/glTF/blob/main/specification/1.0/schema/glTF.schema.json https://json-schema.org/