[InstSimplify] fold icmp with mul nsw and constant operands

https://rise4fun.com/Alive/slvl

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

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

Follow-up to the 'nuw' variation added with:
rGf879c9b7