missing some typeConstraints methods (`<:<` and `=:=` )

[xuwei-k]

https://github.com/scala/scala/blob/a5270194b6eec9678a79e2f88a83d83aa6b92de1/src/library/scala/typeConstraints.scala

• substituteBoth
• substituteCo
• substituteContra
• compose
• andThen
• liftCo
• liftContra
• flip
• antisymm