Add new c8y_LWM2MObserveNotification and c8y_LWM2MSend event types.

Messages originating from the device (Observe Notify and Send) are included in the Event Notification channel but now appear only in the c8y_lwm2mlog event type (that cannot be used as it is not supported).

These 2 new Event types will allow uService logic to interact with these specific types of messages (other C8Y APIs can also be used to query same). [I had to use a work around on the NB API POC work to do this].