[llvm] [ADT] Wrapper for `std::accumulate` accepting a `range`. (PR #158702)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

### Merge activity

* **Sep 16, 2:18 PM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/158702).


https://github.com/llvm/llvm-project/pull/158702