+doc Add more imports to the stream quick start guides for Java and Scala (#20797)

* Add more imports to the stream quick start guides.

This makes it easier for people to execute the code samples while they
read through the guide.

* Change line endings to be consistent with other files

For some reason these 2 files had CR+LF line endings.

akka-docs/rst/scala/code/docs/stream/QuickStartDocSpec.scala

@@ -3,19 +3,22 @@
  */
 package docs.stream
 
-//#imports
+//#stream-imports
 import akka.stream._
 import akka.stream.scaladsl._
-//#imports
+//#stream-imports
+
+//#other-imports
 import akka.{ NotUsed, Done }
 import akka.actor.ActorSystem
 import akka.util.ByteString
-
-import org.scalatest._
-import org.scalatest.concurrent._
 import scala.concurrent._
 import scala.concurrent.duration._
 import java.nio.file.Paths
+//#other-imports
+
+import org.scalatest._
+import org.scalatest.concurrent._
 
 class QuickStartDocSpec extends WordSpec with BeforeAndAfterAll with ScalaFutures {
   implicit val patience = PatienceConfig(5.seconds)