KCM Plasmasearch: Do not intialize runners in config module

Summary:
The runners are loaded from the plugin info list Plasma::RunnerManager::listRunnerInfo(),
because of that there is no need to create a RunnerManager and initialize the plugins.

If you have a lot of additional plugins installed that do a lot of work in the init/reloadConfiguration
method the loading time of the KCM is notable slower.

Additionally the KCMUTILS_VERSION version check has been removed, because
the KF5_MIN_VERSION is 5.69.

Test Plan:
All plugin should show up.
To check this create a debug which prints the length of the listRunnerInfo list.
Then you can verify that the length of the list is equal to the count
of entries in the plugin selector. For this you can also use the xdotool utility:
sleep 5;for i in {1..myNum}; do sleep 0.1;xdotool key Down; done.

Reviewers: Plasma, davidedmundson, ngraham, meven

Reviewed By: ngraham

Subscribers: plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D29319