[llvm] [GlobalOpt] Refactor CleanupPointerRootUsers (PR #84694)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Please clarify the commit title and description to provide more details on the change. `Refactor CleanupPointerRootUsers` makes it sound like there's no change in functionality, but IIUC this adds new functionality.

https://github.com/llvm/llvm-project/pull/84694