[llvm] [LoopUnroll] Simplify reduction operations after a loop unroll (PR #84805)

[Ricardo Jesus via llvm-commits]

rj-jesus wrote:

The failed `clangd` test seems to be unrelated to this transform.
```
Clangd Unit Tests :: ./ClangdTests/DiagnosticTest/RespectsDiagnosticConfig
```

https://github.com/llvm/llvm-project/pull/84805