[ConstantRange] Compute exact no-wrap region w/o materializing CR. (#223969)
Inline logic into makeExactNoWrapRegion() so we do not need to construct
temporary constant ranges.
Together with using makeExecuteNoWrapRegion in SCEV, this improves
compile-time on SCEV-heavy workloads.
Analysis aided by Opus 5.
PR: https://github.com/llvm/llvm-project/pull/223969