CH - Add production readiness as exit criteria

Why is this change being made?

New infrastructure components require going through the production readiness review process to ensure we have enough documentation, observability, and reliability for the service to run at GitLab.com production scale. ClickHouse Cloud as a new service for GitLab.com (and self managed) falls into this process and requires wide collaboration with groups implementing ClickHouse and collaboration between Service Owners, Security and Infrastructure teams. This MR adds it as an Exit Criteria to the CH WG.

Author and Reviewer Checklist

Please verify the check list and ensure to tick them off before the MR is merged.

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the Maintained by section on the page being edited
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  • The when to get approval handbook section explains the workflow in more detail
• For transparency, share this MR with the audience that will be impacted.
  • Team: For changes that affect your direct team, share in your group Slack channel
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