Signal buffer event on audio in/out system stop, and force remove all registered audio buffers

src/audio_core/device/device_session.h

@@ -90,6 +90,11 @@ public:
      */
     void Stop();
 
+    /**
+     * Clear out the underlying audio buffers in the backend stream.
+     */
+    void ClearBuffers();
+
     /**
      * Set this device session's volume.
      *