Make PrimitiveGeometryComponent a more fundamental data structure

[HexaField]

Similar to the MaterialComponent, the PrimitiveGeometryComponent should just be a GeometryComponent that points to the material for the surface, as well as storing the geometry information.

The MeshComponent should be an array of GeometryComponent entities, as per the GLTF spec.

https://github.com/KhronosGroup/glTF/blob/main/specification/2.0/figures/gltfOverview-2.0.0d.png