Standardize output formats to match transformers

[akashsaravanan-georgian]

At present all models return return loss, logits, classifier_layer_outputs.

Transformer models generally return loss, logits, hidden_states, attentions. Maybe we realign with this in the future?

Ref: https://github.com/huggingface/transformers/blob/main/src/transformers/modeling_outputs.py#L665-L699