[llvm] [IVUsers] Make IV-use collection independent of SSA use-list order (PR #215261)

[via llvm-commits]

elle-j wrote:

Tagging @wenju-he (as I saw you previously worked on a [similar issue](https://github.com/llvm/llvm-project/pull/190587), which I also mention in [issue 215260](https://github.com/llvm/llvm-project/issues/215260)).

https://github.com/llvm/llvm-project/pull/215261