some/many on Alternative

Haskell's Alternative has some/many defined as:

some v = (:) <$> v <*> many v
many v = some v <|> pure []

We couldn't add those because without laziness the simple thing doesn't terminate. However, now that we have Defer[F] we can actually write these methods:

  def listOf[A](fa: F[A])(implicit F: Defer[F]): F[List[A]] =
    combineK(map(nonEmptyListOf(fa)(_.toList)), pure(Nil))

  def nonEmptyListOf[A](fa: F[A])(implicit F: Defer[F]): F[NonEmptyList[A]] =
    map2(fa, F.defer(listOf(fa)))(NonEmptyList(_, _))

The issue names Alternative and Defer and proposes listOf and nonEmptyListOf as the entry points; first locate those definitions in the Cats source. Check how existing Alternative operations are tested, then confirm the new methods are available with the intended deferred behavior and covered by tests.