[llvm] [InstCombine] Add fold for fabs(-x) -> fabs(x) (PR #94183)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

@tstellar Should we turn off `Always suggest updating pull request branches`? I think it is misleading to new contributors.

https://github.com/llvm/llvm-project/pull/94183