Automate postgres checkup report

Let's automate running https://gitlab.com/postgres-ai-team/postgres-checkup and produce a new checkup report every week (?). The result can be pasted into an issue in the infrastructure queue and reviewed from there.

An example report led to lots of great insights, e.g. in https://gitlab.com/gitlab-com/gl-infra/infrastructure/issues/6590 et al.