[primTorch] Rewrite nan_to_num ref in terms of aten functions (#93952)
This de-duplicates `_refs.nan_to_num` with the inductor decomposition
and simplifies it to not reimplement `isnan`, `isposinf` and `isneginf`.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/93952
Approved by: https://github.com/lezcano
