Allow custom analytics dashboards in the group scope

Problem

Currently users are able to create custom analytics dashboards for a Project, but not a Group.

Solution

Both the Project and Group scope utilize the same framework, so we should be able to enable the behaviour in the Group scope by removing this condition.

We may see compatibility issues with existing visualizations when trying to render them within a Group analytics dashboard, so we should make this change behind a new group_analytics_dashboard_editor feature flag. Once we've made necessary changes or verified that all listed visualizations work within the Group scope, we'll be able to roll out the feature flag.