Add additional Prometheus instance for different retention period

[MoritzWeber0]

Our default Prometheus retention policy is 1 year:

capella-collab-manager/helm/templates/prometheus/prometheus.deployment.yaml

Line 39 in a46a5cb

- "--storage.tsdb.retention.time=1y"

The more metrics we add, the more storage is needed. Some metrics are valuable and should be stored for 1 year, e.g. T4C license usage.

Other metrics like process metrics of sessions should only be stored for 30 days. Another Prometheus instance should be added for it.

[zusorio]

After doing some research on this, it seems like creating a new prometheus instance might not be the best option.
Instead, we could use a service like Grafana Mimir or Thanos to collect metrics from our prometheus instance. These tools are designed for long-term storage, which means we could store metrics using different retention periods and resolutions.