Improve API for glTF builder

[Carifio24]

The glTF builder exposes a lot of details regarding the particular glTF library that we're using, and requires the user to do a lot of the tedious buffer/view/accessor setup themselves. It would be nice to have this (and all the builders) have very generic APIs where you just add a mesh using points/triangles/color/etc without needing to do all of that.

[Carifio24]

While I still think that this would be nice, the more I do with the GL formats the less I'm convinced that this would be worth it. While the buffer/view/accessor setup is a bit complicated, it also allows us to reuse the same data values multiple times and save file space if we're clever about how we structure things.