kded: Show all marker level warnings in one notification

Mike Noerequested to merge
work/noee/check-for-multiple-markers into master

Currently, marker level checker notifies immediately when the first low marker is found, regardless of how many markers are present and below threshold. So, if, for example, there is an empty black cart and a low color cart, but you'd only see a notification for the first one found low.

In addition, there are some printing devices that have numerous (>4) markers per device, all with exclusive marker levels. This MR adds a small refactor to check all markers for low and consolidate the messages into a single notification.

Testing

Modify printers.conf to have more than one cart and set level on both to 0. See https://invent.kde.org/plasma/print-manager/-/wikis/Testing-with-printers.conf

Screenshot_20251128_081443.png

Merge request reports