A "Select All" option has the value of all the rest of the options combined. Used for the Window Types property.
An Exclusive option cannot be check as the same time as any other options, but uses its own value. Used for "All Activities" and "All Virtual Desktops" properties.
This builds on a refactor of OptionsModel to provide
useFlags as properties
and roles from OptionsModel in C++ side, to simplify the QML part
and improve the treatment of flag-based properties in