[primTorch] Rewrite is{,pos,neg}inf refs in terms of aten functions (#93951)
`isposinf` and `isneginf` currently fallback in inductor. Here, I
enable the existing decompositions to work with inductor.
`isinf` can also be written with aten functions, however I don't add
it to inductor's decompositions because `isinf` is lowered to
`tl.libdevice.isinf` in triton.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/93951
Approved by: https://github.com/lezcano
