DLB: Update Grafana dashboards with new metrics

Context

Related to Container Registry: DLB Phase 1 (&14105 - closed).

Task

Once DLB: Expose new settings in the Distribution He... (#1375 - closed) is merged, we should be able to enable DLB in staging and then update the registry Grafana dashboards with graphs based on the new load balancing metrics. This will be a pre-requisite for a successful production readiness review.

• 1. Temporarily make the registry continue with startup if unable to resolve DLB configs (to prevent disrupting the staging env in case there is a configuration mistake/failure)
• 2. Enable DLB in staging
• 3. Update Grafana dashboards to include new DLB metrics
• 4. Revert 1.