DataFlowManager will be removed and there will be a single instance of the DataFlowController that could be used by
the runtime.
When it was implemented there was this will to have the possibility to run multiple DataFlowControllers in the same runtime.
This feature has never really been used, and the selection mechanism is definitely not necessary, especially now with the
upcoming DataPlane Signaling spec: we can foresee that there will be a single DataPlane protocol used, eventually with
multiple versions, but everything managed by the same flow controller.
DataFlowManager will be removed, and DataFlowController will become an injectable mandatory service.