[Test] Add test showing missing canonicalization opportunity in SCEV

We could have same SCEVs for the following expressions:
  zext(umin(x, y)) and umin(zext(x), zext(y));
  zext(umax(x, y)) and umax(zext(x), zext(y))
  sext(smin(x, y)) and smin(zsxt(x), sext(y));
  sext(smax(x, y)) and smax(sext(x), sext(y)).