Update Model Loading API to 1.21.5

[PepperCode1]

• Add ModelModifier.*BakeItem events. Their utility is currently limited as the render state cannot be inspected, but they will be much more useful after the 1.21.5 FRAPI port.
• Remove ModelModifier.*Bake events as UnbakedModels are not really baked anymore
• ModelModifier.*BakeBlock events now accept a BlockState instead of a ModelIdentifier
• Temporarily remove extra model API. Porting it directly is not possible and more time needs to be spent designing a new API that will cover the same use cases.
• Remove UnwrappableBakedModel as it is potentially less useful with the changes to the model system. It will be re-added later if necessary.
• Add WrapperBlockStateModel which simply delegates all method calls to a different BlockStateModel. This class existed in vanilla in 1.21.4 as WrapperBakedModel but was removed.
• Add WrapperUnbakedItemModel which simply delegates all method calls to a different ItemModel.Unbaked
• Add WrapperItemModel which simply delegates all method calls to a different ItemModel
• Move all model wrapper-related classes to a separate package

[modmuss50]

FYI: Build failuire should be fixed when you merge.

[modmuss50]

Looks really good to my untrained eye, just one small question about the api design.