This method replaces the X-KDE-ORDERING property in the Effect's desktop
files. This change is a preparation step for integrating the new Effect
Loader which doesn't read the ordering information. Thus it needs to be
provided by the Effect itself so that the EffectsHandler can properly
insert it into the chain.

Also for the built-in Effects on the long run it doesn't make much sense
to install the desktop files. And binary plugin effects will migrate to
json metadata which also doesn't have the KService::Ptr. Thus overall it
simplifies to read this information directly from the Effect.