[SCEV] Use AddRec monotonicity in isKnownViaNonRecursiveReasoning. (#218280)
Monotonic AddRecs are never less than their start value; use that in
when reasoning about predicates involving an AddRec and its start value.
Improves results in a few cases on llvm-opt-benchmark-nightly:
https://github.com/dtcxzyw/llvm-opt-benchmark-nightly/pull/996
PR: https://github.com/llvm/llvm-project/pull/218280