Fix crash on exit in kio_file
Summary:
All QTextCodec are deleted by QCoreGlobalData on exit, so they must be allocated on the heap.
Before Qt 5.12, it is even not allowed to delete them.
BUG: 408797
Reviewers: cfeck, dfaure, broulik
Reviewed By: dfaure
Subscribers: aacid, kde-frameworks-devel
Tags: Frameworks
Differential Revision: https://phabricator.kde.org/D24150