staging/redis-svix: Add svix specific configuration

Related to swh/infra/sysadm-environment#5105 (closed)

1. In archive-staging-rke2/redis-svix-config.yaml declare the configmap with the extra parameters.
   Ref: https://github.com/OT-CONTAINER-KIT/redis-operator/blob/master/example/v1beta2/additional_config/configmap.yaml
2. In argocd-configuration/applications/archive-staging-rke2/redis-svix.yaml reference this configmap as redisConfig in helm values.
   Ref: https://github.com/OT-CONTAINER-KIT/redis-operator/blob/master/example/v1beta2/redis-standalone.yaml#L7-L8
3. Additonally define a priroty class.
   Ref: https://ot-container-kit.github.io/redis-operator/guide/redis-config.html#helm-parameters