cloudproviders elide text for recent files activity submenu

[coreyberla]

As part of libcloudproviders, cloudproviderswrapper generates and provides a menu model for the menu to be used in a file manager. Within that menu is a submenu of file activity. Since the file activity includes full filenames, it can be extremely long and cause weird behavior (see linked issue below for Nautilus). I arbitrarily chose to use the main menu width as a baseline for how wide the submenu should be (it can be up to twice as wide).

https://gitlab.gnome.org/GNOME/nautilus/-/issues/2405

I apologize in advance, I don't spend much time programming c++ and have never used qt