Improve some ListenetSet gep descriptions (#3978)

* Improve some ListenetSet gep descriptions

* Add examples of conflicting ListenerSets

* Fix some review findings

* Fix some comments on GEP

* Make the behavior on route attachement explicit

* Fix some reviews

* Use XListenerSet on example kinds

* Final fix on listenerset gep

* Fix some more reviews

* Add clarification on ListenerSet attachment

Author: rikatz