[Bookmarks Runner] Cleanup tests CMakeList
Summary:
Build the test dependencies as static library. Remove duplicate and
commented out lines. Use ecm_add_test instead of setting up everything
manually.
Test Plan: make && ctest
Reviewers: Frameworks, mart
Reviewed By: mart
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D16404