Port kcminit loading away from KServiceTypeTrader
As we have discussed, this mechanism is considered Plasma-internal, meaning that we don't have to keep the KServiceTypeTrader stuff around.
To avoid duplicating the KCMs or having to split the kcminit stuff in a separate binary, symlinks are used to query the available plugins. By having a unified "kcminit" symbol for the function which will get called, we can drop the need for the custom property.
Task: https://phabricator.kde.org/T14335
Prequisite for using only embedded json metadata for the KCMs, see https://phabricator.kde.org/T14517
Draft MR for now, since all the other kcminit providers will need to be ported too.
Edited by Alexander Lohnau