[llvm] [ValueTracking] Refactor `isKnownNonEqualFromContext` (PR #127388)

[Ramkumar Ramachandra via llvm-commits]

https://github.com/artagnon commented:

Could you kindly add the NFC tag to the title. It's not obvious that this patch is an NFC, although the patch summary has an explanation.

https://github.com/llvm/llvm-project/pull/127388