feat: add Grafana dashboards and alerts to monitor Thanos

[lentidas]

Description of the changes

This PR adds multiple Grafana dashboards and Prometheus alerts to monitor Thanos.

The alerts are conditionally deployed depending on the Thanos components deployed. Note that the sidecar rules are always deployed, because the DevOps Stack was designed for Thanos in the sidecar mode and not in the receiver mode. When we change this implementation, we should be aware of that.

Also, for the time being, the dashboards are always deployed, even if certain components are not. Note that certain dashboard files are suffixed with .ignore to disable them. I'll let this be done statically until I figure out a way to do it while still using the iteration over the files in the grafana-dashboard.yaml template.

⚠️ Do a Rebase and merge

Breaking change

• No

Tests executed on which distribution(s)

• AKS (Azure)
• EKS (AWS)
• SKS (Exoscale)