This automatizes the generation of logging categories so a
kdeconnect-kde.categories is generated and installed to
/usr/share/qlogging-categories5/ so kdebugsettings can use it.
Also, sets the default logging level to Warning. So now the logs
of users won't be filled with debug messages but they can
modify the configuration easily with kdebugsettings.
Summary: KDE Connect, now with correct naming!
Test Plan: It still builds.
Reviewers: #kde_connect, apol, nicolasfella
Reviewed By: #kde_connect, apol, nicolasfella
Subscribers: nicolasfella
Differential Revision: https://phabricator.kde.org/D11036
