Add a new `org.osbuild.chown` stage for setting user and group ownershop
of files. The stage runs the `chown` from the image using `chroot` to
enable it to use users and groups that exist only in the (image) tree.
Add unit test testing the stage in various scenarios.
Co-authored-by: Janine Olear <pninak@web.de>
Signed-off-by: Tomáš Hozza <thozza@redhat.com>
16063fff57