[llvm] [InstCombine] Fold -X / -Y -> X / Y (PR #88422)

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AtariDreams wrote:

> The second and third proof seem unrelated? Also the first proof is incorrect w.o the `noundef` i.e: https://alive2.llvm.org/ce/z/22Bers you need to make sure the div will not trigger immediate UB. Please update your code and proofs accordingly.

I fill find out how to deal with those but for now I will opt for the check of no poison or undef

https://github.com/llvm/llvm-project/pull/88422