This rewrites the "Background services" KCM in QML using `ScrollViewKCM`.
The two separate list views are merged into a single one with the configurable services at the top, and the ones that are loaded on-demand and "only for your convenience" at the bottom.
A search field is added searching through name and plugin ID. Since the sortable table headers are gone, a filter combo is provided instead to filter for all, running, or non running services.
As an extra Schmankerl when starting a service that immediately disables itself again (which technically isn't an error that would be indicated as such) a hint is shown to the user so they're not left wondering why it doesn't start.
Furthermore, the code is cleaned up a lot (quite eerie, adding a 2020 Copyright to an existing 2002 one :), ported to json plugin data, and a proper `QAbstractListModel` added.