Automate db creation for praefect on release-environments

What

As part of #19968 (closed), we create a praefect deployment. Unfortunately, there's a manual step that needs to be done: https://docs.gitlab.com/charts/charts/gitlab/praefect/#creating-the-database. This issue is to automate this step.

Why

The helm installation of praefect, will get stuck until the database gets created, thus, the deployment might fail due to timing issue.

How

There are multiple options we can do

• on the PostgreSQL init container we can use initContainer to create the database/fetch the secret from *-praefect-dbsecret and use it
  • this might be tricky though, as the praefect should have been deployed and its secrets are ready.
• As suggested by Graeme, the best option is a custom K8s job with the secrets mounted on it that can run the commands against Postgres.