[FIX] Message view mode setting was missing at user's preferences (#10395)

* This commit brings back the view mode for messages. In addition the name changed from viewMode to messageViewMode to avoid any confusion with sidebarViewMode (+ migration to change name in database as well)

* viewMode field needs to be unset in an extra call, because the first one still works with it.

* - Reverted language file changes for Sidebar_view_mode and Message_view_mode as both still will be translated with View_mode
- Created an own section for Notifications in Account Preferences. Brings View Mode a bith more in context to it's section header
- Optimized migration

* Use update instead of create, because document may already be created by script.

* Fixed lint errors

* Renamed translation "View_mode_info" to "Message_view_mode_info" in all translation files I missed yesterday.

* Removed auto-translations