Configure statement timeout

What does this Merge Request do?

This change configures a statement_timeout for the postgres connection. This should be set, especially during testing. Not necessarily to limit the query time, but rather present the application with a timeout set - because in some cases application behavior is different, when a statement timeout is configured.

An example is gitlab#251084 (closed), where the rake task failed if a statement timeout was present. That was completely invisible in dev and testing, because we don't set a statement timeout there.

Now for CI, we add the setting here: gitlab!42692 (8e462453)

Merge Request checklist

• Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.