As a follow-up to rOMWCf4360b649084: debug.json: List primary DC servers first, we should have the list be automatically sorted so it doesn't require a manual revert+deploy at switchover time.

Since rOMWC2a5e014477ca: noc: Expose primary datacenter on conf/ noc has been able to determine the primary DC by "parsing" yaml, that code could be copied or refactored into a shared function that a PHP script could use to generate debug.json on the fly with servers sorted in the correct order.