Setup counter for Productivity Analytics

What does this MR do?

CE counterpart: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/16431

This commit only contains the Productivity Analytics counter definition and tests.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content