Port away from KDeclarative setup functions

It doesn't do anything useful/relevant for us. The only relevant thing
(setting up the KLocalizedContext) is done anyway
2 jobs for master in 8 minutes and 13 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Build
passed linux kf5-qt5 qt5.15 #114149

00:07:54

85.0%
passed reuse #114148
reuse

00:00:18