Settings page for instance security dashboard

See Design Issue and parent Epic for details.

Implementation Plan

This is the component mentioned: ee/app/assets/javascripts/security_dashboard/components/first_class_project_manager/project_manager.vue

• Split dashboard configuration out into a new Settings page. Here's the related design: #222445[d05_Instance-settings.png].
• Dashboard configuration empty stat would still exist on both Security Dashboard and Vulnerability Report pages but the Edit Dashboard button would no longer appear.
• Add Projects button would now go to the Settings page instead of rendering in place.