Cluster update metrics

Metrics that are used to generate cluster update alerts are added to the alerting rules in /var/lib/prometheus/alerts/backend.rules. These metrics are described in the table:

Metric	Description
softwareupdates_cluster_info	Currently installed version and available version for the cluster
softwareupdates_cluster_available	Update availability for the cluster
softwareupdates_node_uptodate	Shows if a specific node is updated to the latest version
softwareupdates_node_available	Shows update availability for a specific node, currently installed version and available version, and if a node reboot is required
softwareupdates_node_info	Currently installed version and available version for a specific node