[AppNavigation] [Tabs] - new listener is added on tabsRouters despite some routers already have a listener

[DMouayad]

Description:

• Because adding a new tab results in creating a new GoRouter instance and we need to listen to changes on this router:
  a new listener is added for every tab-router even if we already added a listener on it.
• Current implementation removes the listener before adding a new one but it seems to not have any effect i.e. doesn't remove existing listener.

Suggestions:

• create a list of keys, each key belongs to a GoRouter instance.
• we acquire the keys from the object hashCode.