Archives: Rename three KConfigGroups to make things clearer

Rename two KConfigGroups named confGrp to dependGrp, and a KConfigGroup named config to dependGrp, because they only operate with the "Dependencies" group. That also easies keeping code synchronized.

Test plan: The one described in the task Solve some bugs related to archives, remove some duplicated code.

Differential Revision: https://phabricator.kde.org/D28415