KadeModeMenuList: fix memory leaks and others
Summary:
- Remove strings m_searchName in the destructor of the ListItem class.
- Use the same object for transparent colors/icons.
- Add the Deselect flag in item sections.
Reviewers: KTextEditor, dhaumann, cullmann
Reviewed By: KTextEditor, cullmann
Subscribers: kwrite-devel, kde-frameworks-devel
Tags: Kate, Frameworks
Differential Revision: https://phabricator.kde.org/D24210