[llvm] [Transforms][Utils] Add LoopSplitUtils for iteration-space loop splitting (PR #205995)

[Ramkumar Ramachandra via llvm-commits]

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artagnon wrote:

```suggestion
#define DEBUG_TYPE "loop-split-utils"
```

I don't think we need a separate DEBUG_TYPE for the test-pass? It would make working with `opt -debug-only` more intuitive to work with?

https://github.com/llvm/llvm-project/pull/205995