Cofree.cata is not stack-safe

[road21]

This throws java.lang.StackOverflowError (code from tests CofreeSuite but with bigger size)

val unfoldedHundred: Cofree[Option, Int] = Cofree.unfold[Option, Int](0)(i => if (i == 1000000) None else Some(i + 1))

  val cata =
    Cofree
      .cata[Option, Int, NonEmptyList[Int]](unfoldedHundred)(
      (i, lb) => Eval.now(NonEmptyList(i, lb.fold[List[Int]](Nil)(_.toList)))
    ).value

Eval.defer can easily fix this:

def cata[F[_], A, B](cof: Cofree[F, A])(folder: (A, F[B]) => Eval[B])(implicit F: Traverse[F]): Eval[B] =
    F.traverse(cof.tailForced)(c => Eval.defer(cata(c)(folder))).flatMap(folder(cof.head, _))