Prefer data-error/warning/information icons over dialog-* for line marker
The data-* icons are introduced with Breeze/Oxygen icons of KF 5.68, with the purpose to be status icons to be used as
Old:
New:
See https://phabricator.kde.org/D27272 for motivation to introduce these. In KDevelop these new icons will appear e.g. like this:
