allow eval metrics to be passed in to HuggingFaceModel directly

[dakinggg]

What does this PR do?

Previously HuggingFaceModel automatically used metrics for both train_metrics and eval_metrics. This can cause an issue if using Evaluators with metrics that can't be applied during training (e.g. ICL metrics). Now, if you pass in eval_metrics, it will use that for eval_metrics instead.

What issue(s) does this change relate to?

CO-1788

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[nik-mosaic]

Great PR. Nice, simple code. Approved!