Ensure internal events aren't pushed into central event bus

[cburgdorf]

What was wrong?

Currently, even if we would broadcast an event only to our very own Endpoint it will still go on a roundtrip to the EventBus (which usually should sit in another process) which is

a.) a waste of resources

b.) restricts use case to pickable events

If we would short circuit internal events to stay within the Endpoint we could get rid of the special legacy PluginManager events in Trinity and handle those via the event bus as well.

How can it be fixed?

Detect internal events and ensure they stay within the Endpoint.