Implement Post Initialized State Startup of EventHandler

[bakerstu]

During node initialization, all of an EventHandler's identified callbacks are called. This ensures that the identified messages get sent out on the bus. However, these callbacks do not get called if an EventHandler is created after the node has already been initialized.

There should be logic to detect if the node is already initialized during construction, and if so, trigger the identified callbacks to get called from the constructor.