[llvm] [StructurizeCFG] Introduce struct PredInfo. NFC. (PR #115457)

[Juan Manuel Martinez Caamaño via llvm-commits]

https://github.com/jmmartinez approved this pull request.

Thanks ! I've should have done this in the first place instead of using `using ValueWeightPair = std::pair<Value *, MaybeCondBranchWeights>;`.

https://github.com/llvm/llvm-project/pull/115457