Move ozone to new subdirectory

Move ozone related files to core/ozone.
Split classes so they can be reused for new
ozone platform backends.

Change-Id: I98a2aac6807ef2b3eee92eea9ecfd8fce6dd9d16
Reviewed-by: Kai Koehne <kai.koehne@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>