What does this MR do and why?

Adds a new element with the top-level namespace's full name, type, visibility level icon and avatar to the Usage Overview panel on the Value Stream Dashboard.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

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Before	After

How to set up and validate locally

1. Please make sure you have a GitLab Ultimate license.
2. Feature.enable(:group_analytics_dashboard_dynamic_vsd)
3. Create a new (or choose an existing) top-level group and invoke the seed script: GROUP_ID=<group-id> FILTER=vsd_overview_counts SEED_VSD_COUNTS=1 bundle exec rake db:seed_fu
4. Navigate to the group above and, from the left sidebar, click the Analyze > Analytics dashboards link
5. The group dashboard list should appear, select Value Stream Dashboard
6. Verify that the top-level namespace and related elements appear in the Usage overview panel.

Related to #439699 (closed)