Fix GDB/LLDB unit tests to use KSharedConfig instead of separate KConfig
Summary:
Avoids issues with sync'ing from file-system between the different
working memory config instances
Reviewers: KDevelop, qi437103
Subscribers: kdevelop-devel
Tags: KDevelop
Differential Revision: https://phabricator.kde.org/D14365
(cherry picked from commit e559126089651c33e3f560949e34991cd90759bb)