ci: Refresh contents

ci: Refresh contents

Notable changes:

  * the CentOS Stream 8 container is now using a proper base
    image instead of starting from a CentOS 8 image and then
    adding the CentOS Stream 8 repositories on top;

  * distributions that have a perl-base package are now using
    that one instead of the regular perl package, which
    contains a bunch of features we don't need, resulting in
    smaller containers.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>