[llvm] [SCEV] Handle backedge-count logic for std::reverse like loops (PR #92560)

[via llvm-commits]

mrdaybird wrote:

@efriedma-quic Added the rhs wrap check. Alive2 proof:https://alive2.llvm.org/ce/z/f2CpXv
For future reference, what other cases do you think we could handle here?

https://github.com/llvm/llvm-project/pull/92560