Hardening of typed./ClusterShardingSpec, #25794

* The replies didn't change after the leaving
* I see two reason why it could have failed
  * The test is sending the same messages as the very first thing
    earlier in the test and then sharding might not now about the
    two nodes and therefore allocated all to one node
  * All messages are hashed to the same node/shard

akka-cluster-sharding-typed/src/test/scala/akka/cluster/sharding/typed/scaladsl/ClusterShardingSpec.scala

@@ -393,13 +393,13 @@ class ClusterShardingSpec extends ScalaTestWithActorTestKit(ClusterShardingSpec.
     }
 
     "use the stopMessage for leaving/rebalance" in {
-      var replies1 = Set.empty[String]
-      (1 to 10).foreach { n ⇒
-        val p = TestProbe[String]()
-        shardingRef1 ! ShardingEnvelope(s"test$n", WhoAreYou(p.ref))
-        replies1 += p.expectMessageType[String]
+      // use many entites to reduce the risk that all are hashed to the same shard/node
+      val numberOfEntities = 100
+      val probe1 = TestProbe[String]()
+      (1 to numberOfEntities).foreach { n ⇒
+        shardingRef1 ! ShardingEnvelope(s"test$n", WhoAreYou(probe1.ref))
       }
-      replies1.size should ===(10)
+      val replies1 = probe1.receiveN(numberOfEntities, 10.seconds)
 
       Cluster(system2).manager ! Leave(Cluster(system2).selfMember.address)
 
@@ -408,13 +408,11 @@ class ClusterShardingSpec extends ScalaTestWithActorTestKit(ClusterShardingSpec.
         Cluster(system2).isTerminated should ===(true)
       }
 
-      var replies2 = Set.empty[String]
-      (1 to 10).foreach { n ⇒
-        val p = TestProbe[String]()
-        shardingRef1 ! ShardingEnvelope(s"test$n", WhoAreYou(p.ref))
-        replies2 += p.expectMessageType[String](10.seconds)
+      val probe2 = TestProbe[String]()
+      (1 to numberOfEntities).foreach { n ⇒
+        shardingRef1 ! ShardingEnvelope(s"test$n", WhoAreYou(probe2.ref))
       }
-      replies2.size should ===(10)
+      val replies2 = probe2.receiveN(numberOfEntities, 10.seconds)
       replies2 should !==(replies1) // different addresses
     }
   }