Models inside of subfolders can be seen in the models view but not removed

[cebtenzzre]

GPT4All searches subfolders of the data directory for models. However, it also assumes that all models are in the root of the data in many parts of the code, by using the data dir itself instead of the dirpath field of ModelInfo. This causes actions such as the "Remove" button to not work.

Fix buried somewhere in #3034, but that is on hold due to other priorities.