WIP: Port away from KSettings::Dispatcher

This depends on frameworks/kcmutils!51

KF6 task: https://phabricator.kde.org/T13695
2 jobs for master in 5 minutes and 5 seconds (queued for 87 minutes and 40 seconds)
Status Name Job ID Coverage
  Build
passed build_clazy_clang_tidy #114829

00:02:26

passed linux kf5-qt5 qt5.15 #114828

00:02:38

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