CpsTreeScope

append cps tree, which is frs and then snd. we use this representation instead Mapped/Flatmapped in cases, where we later can apply await to append term and simplify tree instead wrapping awaited tree in extra flatMap

when we have swhifted function, which should return F[A] but we want to have in F[A] methods with special meaning, which should be performed on F[_] before jumping into monad (exampe: Iterable.withFilter) we will catch in ApplyTree such methods and substitute to appropriative calls of shifted.

represent select expression, which can be in monad or outside monad.

constructor is not devoted to used directly: use SelectTypeApplyCpsTree.create instead. selects is reversed (i.e. external added to head)