Add overload to prepend actions to the "Actions" menu
This will allow us to add QActions to the "Actions" submenu This way we can utilize existing actions and o not clutter our menu.
See https://phabricator.kde.org/T13752 for the discussion on this topic and system/dolphin!81 (merged) for a dolphin implementation.
I am not so sure about the separator:
If we want to remove that we need to do that in this MR.
If you agree with the general idea I would make a follow-up MR which will also allow plugin based service menus to be displayed in the actions submenu. I specifically have the compress menu in mind ;)