Save a labels.txt in the artifact directory for the ImageFolderDataset (could maybe apply to other datasets)

[aurelien-clu]

Feature description

Training a model should also provide a way to know the label name and ordering without knowledge of the dataset. It would also prevent potential errors if we default to use the labels provided inside the artifact directory next to the model weights.

Feature motivation

I am training a model that classifies kanjis with many classes (~5600) and no obvious label ordering so it could be prone to error between a prediction [0.1, ..., 0.5] and knowing that this means:

一: 0.1
...
龠: 0.5