Source code - New metrics that only include human users

In https://gitlab.com/gitlab-data/analytics/-/issues/23911, we discovered that some metrics that are relied upon in analysis count non-human users. We would like new metrics instrumented that only count human users. We don't need to remove the existing metrics, as it is also useful to see activity that includes non-human users.

Here are the metrics that are owned by groupsource code:

• usage_activity_by_stage_monthly.create.action_monthly_active_users_project_repo