[InstSimplify] fold icmp with mul nuw and constant operands

https://rise4fun.com/Alive/pZEr

  Name: mul nuw with icmp eq
  Pre: (C2 %u C1) != 0
  %a = mul nuw i8 %x, C1
  %r = icmp eq i8 %a, C2
    =>
  %r = false

  Name: mul nuw with icmp ne
  Pre: (C2 %u C1) != 0
  %a = mul nuw i8 %x, C1
  %r = icmp ne i8 %a, C2
    =>
  %r = true

There are potentially several other transforms we need to add based on:
D51625
...but it doesn't look like there was follow-up to that patch.