Add crossplane tags for namespace and cluster

[leonorfmartins]

For databases created via crossplane, the only possible way to know which namespace and cluster they belong to is if we parse the name, which is not reliable. We should have this meta information in tags.

This way, we can reliably join the DB cost metric with tanka metrics to get a cost breakdown by namespace / team / sku.

Things to consider

• tags should not recreate the crossplane resource. I don't think adding a tag causes it, but we should verify this in dev
• we should enforce future DB instances to have namespace and cluster by default: we could consider a conftest policy checking this.

[leonorfmartins]

We need to also add those tags to terraform, so we can later populate them so they can be surfaced via this metric: https://ops.grafana-ops.net/goto/af0cflzuql8g0c?orgId=1