Improve token order checking with bit masking

[Ssimonas]

Pseudo code for such improvement:

var map[Token]string {
  WETH: "WETH",
  USDC: "USDC",
...
//do not include Stable and Native
}
func (t Token) Elements() (elements []string) {
  for i := 0; i < 32; i++ {
    bit := 1<<i
    if name, ok := map[bit]; ok && t & bit != 0 {
        elements = append(elements, name)
    }
  }
}

func (v ...) CheckOrder(token0, token1 Token) bool {
  return checkToken(v.Token0, token0) || checkToken(v.Token1, token1)
}

func checkToken(token string, mask Token) bool {
  elements := mask.Elements()
  return token in elements
}