Add info popover to the Value stream dashboard - Usage overview panel

What does this MR do and why?

Adds a popover to the panel title that provides supplementary information about the panel metrics

MR acceptance checklist

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Before	After

How to set up and validate locally

1. Make sure you have an Ultimate license
2. Feature.enable(:group_analytics_dashboard_dynamic_vsd)
3. Invoke the seed script: FILTER=vsd_overview_counts bundle exec rake db:seed_fu
4. Verify that count records are created in the console: Analytics::ValueStreamDashboard::Count.count
5. Navigate to the VSD for the group of your choice: (ex. http://gdk.test:3000/groups/gitlab-org/-/analytics/dashboards/value_streams_dashboard)

Related to #435515 (closed)