Ceph 18.* adds acluster label to all Prometheus metrics. When upgrading from earlier releases, historical metrics lack this label and are excluded by Grafana queries that strictly match oncluster. Update the shared Grafana matcher logic to use a regex matcher that also matches series without thecluster label, restoring visibility of pre-upgrade metrics while preserving multi-cluster behavior.

Fixes:https://tracker.ceph.com/issues/74342

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