Previously, Messenger was `Start`ed multiple times, which resulted in
the shutdown process not being invoked on previously initialized
Messenger's sub-instances. This led to the failure of MVDS instance
shutdown causing massive error logs due to the attempts to read from a
closed database.
* feat: Marking Mentions and Replies AC notifications as read also marks corresponding message as seen
* feat: Marking message as seen marks as read corresponding notification (if there is so)
* chore: make messenger activity center test less flaky
* Update VERSION
This creates a smoother experience for users when they leave a community since they can see the exact same messages they had before without having to rely on the mailserver.