[Task Manager] Add "Places" for entries belonging to a file manager

Since we cannot have dynamic jump list actions but this is an often requested feature and common
among other desktop environments, at least add the "Places" to entries belonging to a file manager.

To avoid the menu becoming too long, the number of places shown is limited to 5* when the
application is running and the menu would also have window controls. For when it's a launcher,
all places are shown as there the menu is less likely to become massive.

This is added to services that contain the "FileManager" category, such as Dolphin.

*) It actually truncates it to 5 entries only if there's more than 7 places.
There's nothing more frustrating than having a "reveal more" button that ends up adding just one
or two items once clicked.

Differential Revision: https://phabricator.kde.org/D3815