Add convenience method to start timer without key (#27875)

* Add convenience method to start timer without key

It is probably common that there is no need to allow different timers
that send the same message, and this makes that more convenient to write.

Updated one method to gather feedback, if we like the change I can apply
it to the others as well.

* Add alternative to all typed timer API's

Update java/scaladoc, update tests

Not updated classic actors and FSM API's

akka-docs/src/test/java/jdocs/typed/tutorial_5/DeviceGroupQuery.java

@@ -78,7 +78,7 @@ public class DeviceGroupQuery extends AbstractBehavior<DeviceGroupQuery.Command>
     this.requestId = requestId;
     this.requester = requester;
 
-    timers.startSingleTimer(CollectionTimeout.class, CollectionTimeout.INSTANCE, timeout);
+    timers.startSingleTimer(CollectionTimeout.INSTANCE, timeout);
 
     ActorRef<Device.RespondTemperature> respondTemperatureAdapter =
         context.messageAdapter(Device.RespondTemperature.class, WrappedRespondTemperature::new);