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

[Ashutosh Nema via llvm-commits]

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nema-ashutosh wrote:

Affineness is already enforced in analyzeInduction. Kept the explicit check since we still need the add-recurrence object afterward.

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