feat: add thanos for prom HA

[srodenhuis]

This PR adds Thanos for Prometheus HA and includes:

• add Thanos Helm chart
• configure Prometheus to use Thanos sidecars
• create objstore.yml for OBJ configuration based on configured OBJ provider
• add thanos-query datasource to all Grafana's
• add Thanos Grafana dashboards to Platform Grafana

Testing

• Configure OBJ with a bucket for thanos
• Activate Thanos app
• Check to see if the thanos sidecar is added to the Prometheus pod
• Check (using the Thanos query UI) to see if the sidecar endpoint status is up
• Check if (this can take some time) if the Store endpoint (only one) has status Up
• Set the replica's for prometheus to 2
• Check to see if the second sidecar endpoint comes up
• Check to see if all the announced LabelSets (for both replica's) are shown

You should now see the following:

Checklist

• The values-schema.yaml file and test/** fixtures have been updated to reflect code changes, if applicable.
• The OpenApi Schema from redkubes/otomi-api project is compatible with definitions from values-schema.yaml file, if applicable.
• Helm releases are meeting otomi's baseline security policies, if applicable.