[InstCombine] add more folds for unsigned overflow checks

 ((Op1 + C) & C) u<  Op1 --> Op1 != 0
 ((Op1 + C) & C) u>= Op1 --> Op1 == 0
 Op0 u>  ((Op0 + C) & C) --> Op0 != 0
 Op0 u<= ((Op0 + C) & C) --> Op0 == 0

https://alive2.llvm.org/ce/z/iUfXJN
https://alive2.llvm.org/ce/z/caAtjj

  define i1 @src(i8 %x, i8 %y) {
    ; the add/mask must be with a low-bit mask (0x01ff...)
    %y1 = add i8 %y, 1
    %pop = call i8 @llvm.ctpop.i8(i8 %y1)
    %ismask = icmp eq i8 %pop, 1
    call void @llvm.assume(i1 %ismask)

    %a = add i8 %x, %y
    %m = and i8 %a, %y
    %r = icmp ult i8 %m, %x
    ret i1 %r
  }

  define i1 @tgt(i8 %x, i8 %y) {
    %r = icmp ne i8 %x, 0
    ret i1 %r
  }

I suspect this can be generalized in some way, but this
is the pattern I'm seeing in a motivating test based on
issue #52851.

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