Allow CachedModelDependencyContainer to cache models with non-bindable fields

[smoogipoo]

This container is very strict as to what sort of shape the model it contains should have, and rightfully so because it exposes a "shadow" model to the hierarchy so it can't ensure non-bindable data remains consistent.

But my current path for multiplayer is to remove these bindables bit by bit so as to not generate gigantic PRs, but this conflicts with the shape this container expects. At the end of it all, I hope to remove this container from multiplayer entirely.

So I've made it a bit more lenient by removing the static ctor and safeguarding for non-bindable members.