qt/networkdevicemodel: Add 'maximumCount' and sorting support

This MR adds a 'maximumCount' property to the NetworkDeviceModel and the 'hasMoreItems' property to query whether we have more items to be shown. It also adds sorting capabilities through sortCriteria and sortOrder and a dummy filtering to be used in conjunction with a SortFilterProxyModel, the comprehensive version shall be implemented in an upcoming MR.

This paves the way to capped QML Grid / List views à la Spotify that can display an excerpt of the devices, while proposing to expand the view if needed.

The following branch can be used for testing: https://code.videolan.org/bunjee/vlc/-/commits/dev-listB