Api cleanup

[constantinpape]

I went ahead and cleaned up the function signatures related to both LoRA and 3D models. This will need some changes in your code to account for this (and I will wait with merging so that you can check the changes, I pinged you in some of the most important places in the code). But this now has a more unified interface, especially for the 3d models, which use the same function signatures as the original SAM model, making compatibility of the training code easier.

cc @anwai98 @lufre1 @caroteu

[constantinpape]

Also, I created a new submodule models and moved everything related to custom models there, + created some unit tests for them.

[constantinpape]

Thanks for checking everyone, I will go ahead and merge!