[ConfigModule] Allow creating KCMs without KAboutData
This adds a new constructor that receives a KPluginMetaData instance. This metadata contains all the information needed to replace the usage of KAboutData.
Unfortunatly we cannot use the existing ctor that takes KPluginMetaData since the parameters are in a different order than KPluginFactory expects.
Internally it is checked whether the KCM has been instantiated with a KPluginMetaData and falls back to KAboutData otherwise