Share broker/producer instances among all streams

The current quick and dirty implementation still creates new instances
but replaces them immediately with the shared ones. This should be
improved.

src/AsapoWorker/application.py

@@ -25,6 +25,9 @@ class Application:
         self.worker_class = worker_class
         self.consumer_class = consumer_class
         self.producer_class = producer_class
+        self.receiver_broker = None
+        self.sender_broker = None
+        self.sender_producer = None
         self.executor = ThreadPoolExecutor(max_workers=16)
         self.lock = Lock()
         self.verbose = verbose
@@ -100,9 +103,21 @@ class Application:
         consumer = create_instance_from_configurable(
             self.consumer_class, self.options["receiver"])
 
+        if self.receiver_broker:
+            consumer.broker = self.receiver_broker
+        else:
+            self.receiver_broker = consumer.broker
+
         if self.producer_class:
             sender = create_instance_from_configurable(
                 self.producer_class, self.options["sender"])
+            if self.sender_broker:
+                assert self.sender_producer is not None
+                sender.broker = self.sender_broker
+                sender.producer = self.sender_producer
+        else:
+                self.sender_broker = sender.broker
+                self.sender_producer = sender.producer
         else:
             sender = None