CentOS Stream 10 images are available for master and stable/2026.2 [1]. Add variable `ipa_images_upstream_os` to let operators choose the CentOS Stream version of these images. [1] https://tarballs.opendev.org/openstack/ironic-python-agent/dib/files/ Change-Id: Icfbc3531d998234cbb90d9fb964ccb887b9368cd Signed-off-by: Pierre Riteau <pierre@stackhpc.com>