[llvm] [DA] Rewrite Banerjee MIV test with SCEV-based interval arithmetic (PR #207662)

[Ruoyu Qiu via llvm-commits]

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cabbaken wrote:

Thanks, the wording was unclear.
I’ve rewritten the comment to state the sign conditions. The coefficients of the two terms are `(A - B)` and `-B`, so the sign condition on `B` is reversed.
I also renamed the helper to `strictDirectionIntervalWithUnknownUpperBound`, which better describes its purpose.

https://github.com/llvm/llvm-project/pull/207662