Change the default locale to `C.UTF-8` for RHEL-9.0.
For all the images which install `langpack-en`, keep using the
`en_US.UTF-8` locale. `C.UTF-8` is used as the default for:
- edge-commit
- edge-container
- image-installer
- qcow2
- tar
Also change the default locale for the edge-simplified-installer
installer-tree pipeline, since its package set contains only
`glibc-minimal-langpack`.
Regenerate RHEL-90 and c9s image tests.
Fix#2206
Signed-off-by: Tomas Hozza <thozza@redhat.com>
