Decouple the usage of model_path in model train

[RobotSail]

Presently, the usage of the model_path parameter in ilab train is split between different responsibilities:

• Used as a HuggingFace model reference, e.g. <namespace>/<repo-name>
• Used to reference where the local model will be saved and read from

These should be different parameters to decouple responsibility.

[RobotSail]

Wrong repo