Pseudo-asynchronous mode not working

[mageofboy]

There is currently a couple of issues when using the simulator mode is set to 'pseudo-asynchronous'.

1. send_pickle deprecated. fixed in: [Bug] Replace send_pickled in CARLA drivers #233 (comment)
2. KeyError when releasing sensor data
   
   The issue seems to be because at a certain timestamp, the camera operator is releasing the sensor data (in release_data) before the sensor data has finished processing (in process_images). Therefore, the message at a timestamp is not in self._pickled_messages when we try to access, and the message is only added afterwards.
   The following screenshots display the sequence causing the error:
   
   
   
   It seems like the issue is related to how long it takes for a sensor to be processed. For instance, the depth camera operator has the issue much more frequently than other ones.

[pschafhalter]

Regarding (2), it looks like the planning pose synchronizer operator waits on notifications from the notify_lidar_stream instead of notify_depth_stream.