Keep tests/ and icons/ but put the rest into the toplevel.
The previous setup was so different from the rest of the bunch that
it regularly stuck out in maintenance tasks.
Change-Id: I69821be6268f69682353a388f6bb1fa343215303
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>
