fix(monitoring): Migrate Grafana to grafana-community chart and fix PVC deadlock

[ybezsonov]

Summary

Fixes the workshop bootstrap failure in the performance-platform setup, where Grafana could not be installed/upgraded via Helm. Two independent root causes, both in the setup scripts (infra/scripts/setup/monitoring.sh and infra/scripts/setup/perf-platform.sh):

1. Deprecated Helm chart. As of March 16, 2026 Grafana Labs forked their Helm charts to grafana-community/helm-charts. The grafana chart in the old grafana.github.io/helm-charts repo is now deprecated: true and frozen at chart 10.5.15 (Grafana 12.3.1), so installs printed WARNING: This chart is deprecated.

2. PVC deadlock on upgrade. The chart defaults to deploymentStrategy: RollingUpdate, but the workshop enables persistence on a gp3 EBS volume (ReadWriteOnce). On the plugin upgrade in perf-platform.sh, RollingUpdate starts the new pod before deleting the old one; the new pod cannot attach the RWO volume still held by the old pod, so it hangs until helm --wait hits its deadline: UPGRADE FAILED: context deadline exceeded.

Changes

• Point the grafana chart at the maintained community repo grafana-community/grafana (chart 12.7.2 / Grafana 13.1.0) in both scripts.
• Keep the original grafana repo in perf-platform.sh for grafana/pyroscope, which was not moved to the community repo.
• Set deploymentStrategy.type: Recreate in the Grafana values so the old pod is torn down first and releases the EBS volume. Persisted on the release, so perf-platform.sh inherits it via --reuse-values.
• Raise the plugin-install --timeout from 5m to 10m to cover the EBS detach/reattach cycle plus plugin download on the Recreate path.

Verification

• Confirmed the old grafana chart is deprecated: true and the community repo serves an active grafana chart (12.7.2).
• Confirmed pyroscope still resolves only from the old repo.
• Confirmed every values key the scripts pass (admin.existingSecret/userKey/passwordKey, service, persistence, resources, sidecar.dashboards/datasources, plugins, grafana.ini) exists in the community 12.7.2 chart.
• bash -n passes on both scripts. CI green (the one flaky failure was a transient Maven Central 403 on spring-boot-starter-parent:4.1.0, unrelated to these changes; cleared on re-run).