[ConstraintElim] Use isKnownNonNegative for condition transfer. (#72879)

Use isKnownNonNegative for information transfer. This can improve
results, in cases where ValueTracking can infer additional non-negative
info, e.g. for phi nodes.

This allows simplifying the check from
https://github.com/llvm/llvm-project/issues/63126 by
ConstraintElimination. It is also simplified by IndVarSimplify now; note
the changes in llvm/test/Transforms/PhaseOrdering/loop-access-checks.ll,
due to this now being simplified earlier.