Add shared dashboard listing to the group level

Problem to solve

With Replace product analytics dashboard listing wit... (#388557 - closed) projects will have a shared dashboard listing but it will not exist for groups.

Final solution

We need to add the shared dashboard listing to the group-level.

Implementation plan

frontend / backend

Behind the group_analytics_dashboards feature flag

1. Create a new HAML file in ee/app/views/groups/analytics to add the Vue anchor point #js-analytics-dashboards-list-app copying the data from ee/app/views/projects/analytics/dashboards/index.html.haml.
2. Update ee/app/assets/javascripts/analytics/analytics_dashboards/components/dashboards_list.vue to retrieve dashboards from the group-level rather than project-level.
   • TODO: Figure out more detailed steps and backend changes
3. Update unit tests at ee/spec/frontend/analytics/dashboards.
4. Moved to #417771 (closed) Copy feature spec from ee/spec/features/projects/analytics/dashboards_spec.rb and put it at ee/spec/features/groups/analytics/dashboards_spec.rb and update to check the group-level dashboard
   • Opportunity to DRY this and move shared logic to shared examples