Switch CIT and model loading to use FAPI systems

[SHsuperCM]

With the amount of changes to model loading implementation throughout versions, it feels necessary to migrate from injecting directly in minecraft's model loading to using proper fabric api procedures such as reload listeners for CITs and model loading plugins for models that CITs require. This is especially true for the latest 1.21.2 drop which requires me to completely rewrite and keep a secondary approach to injecting the models into the game.