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

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

Could you kindly rebase the branch or merge main, just to make sure that nothing has changed, before we land this?

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