Find a way to convert Gltf primitive mesh and material to a simplified CPU buffer for rendering

Currently, both Unreal and O3DE has a very similar way to load Gltf. That is it only cares about creating rendering resources from Gltf Primitive and Material. Even though the data structure for GPU resources maybe different, the CPU representation is almost similar with a `vector positions`, `vector normals`, `vector tangents`, etc... If we can find a way to do that work in Cesium Native, the integration is simplified alot on Engine side as they just need to load all those CPU buffers into GPU. This observation is only based on Static Mesh. I'm not sure about Animation and other stuffs though

Start by comparing how Unreal and O3DE load glTF primitives and materials, focusing on the static-mesh case described in the issue. Define the Cesium Native CPU representation for positions, normals, tangents, and related buffers, while clarifying whether animation is in scope. Done means engine integrations can load the simplified CPU buffers into GPU resources.

Written by the indexing model from the issue text.