[InstCombine] improve folds for icmp with multiply operands (PR47432)

[InstCombine] improve folds for icmp with multiply operands (PR47432)

Check for no overflow along with an odd constant before
we lose information by converting to bitwise logic.

https://rise4fun.com/Alive/2Xl

  Pre: C1 != 0
  %mx = mul nsw i8 %x, C1
  %my = mul nsw i8 %y, C1
  %r = icmp eq i8 %mx, %my
  =>
  %r = icmp eq i8 %x, %y

  Name: nuw ne
  Pre: C1 != 0
  %mx = mul nuw i8 %x, C1
  %my = mul nuw i8 %y, C1
  %r = icmp ne i8 %mx, %my
  =>
  %r = icmp ne i8 %x, %y

  Name: odd ne
  Pre: C1 % 2 != 0
  %mx = mul i8 %x, C1
  %my = mul i8 %y, C1
  %r = icmp ne i8 %mx, %my
  =>
  %r = icmp ne i8 %x, %y