Resolve "Create New Security Dashboard (Behind Feature Flag)"

What does this MR do and why?

This change introduces a new version of the Group Security Dashboard behind a feature flag called "groupSecurityDashboardNew".

It also adds the previously created "Open Vulnerabilities Over Time" chart to the dashboard. It is currently only set up with mock data, but this will be changed in future iterations.

References

Screenshots or screen recordings

Before	After (with FF enabled)

How to set up and validate locally

1. Navigate to a group's, project's and instance-level's security dashboard
2. Verify that they all render correctly and there are no changes
3. Enable the group_security_dashboard_new feature flag: http://gdk.test:3000/rails/features/group_security_dashboard_new
4. Verify that the dashboard on the group-level shows the new dashboard
5. The project and instance-level should not be affected

MR acceptance checklist

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

Related to #542373 (closed)