Turn ListenersBroker into a component

ListenersBroker hosts node-local state about what notification streams have been defined. At the end of the day, it it has three distinct parts:

• dataChangeListeners, backed by DOMDataTreeChangeService
• notificationListeners, backed by DOMNotificationService
• deviceNotificationListeners, backed by NETCONF mounted devices

This is a ClassLoader singleton, accessed via static ListenersBroker.getInstance() – which is completely wrong, as it should be a a normal singleton managing the contents of ietf-restconf-monitoring streams' content, with the three parts managed separately as:

• SalRemoteImpl, which handles dataChangeListeners and notificationListeners
• OdlDeviceNotificationImpl, which handles deviceNotificationListeners

This deals with the first part of the problem: getting rid of ListenersBroker.getInstance() and properly injecting the appropriate service into all components accessing ListenersBroker instances.