[llvm] [ctxprof] Scale up everything under a root by its `TotalRootEntryCount` (PR #136015)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

### Merge activity

* **Apr 21, 11:41 AM EDT**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/136015).


https://github.com/llvm/llvm-project/pull/136015