[llvm] [DominanceFrontier] make iterating dereferenced DominanceFrontierBase::find deterministic (PR #69711)

[Jakub Kuderski via llvm-commits]

https://github.com/kuhar approved this pull request.

LGTM. Because this is a piece of core infra, I'd give it another 24h before landing to see if anyone spots potential issues.

https://github.com/llvm/llvm-project/pull/69711