[llvm] IROutliner: Use ValueMapper to remap constants in a function (PR #134850)

[Matt Arsenault via llvm-commits]

arsenm wrote:

### Merge activity

* **Apr 10, 4:29 PM EDT**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/134850).


https://github.com/llvm/llvm-project/pull/134850