[InstCombine] Fold ult(add(x,-1),c) -> ule(x,c) iff x != 0 (PR57635)

Alive2: https://alive2.llvm.org/ce/z/sZ6wwS

As detailed on Issue #57635 and #37628 - for unsigned comparisons, we can compare prior to a decrement iff the value is known never to be zero.

Differential Revision: https://reviews.llvm.org/D134172