Update existing analytics dashboards to use the dashboard layout framework

What does this MR do and why?

• Deleted analytics_customizable_dashboard.vue and gridstack_wrapper component as this can be directly replaced by gl-dashboard-layout
• Updated analytics_dashboard.vue to render gl-dashboard-layout directly instead of analytics_customizable_dashboard.vue
• Updated storybook
• Fixed specs

References

Update existing analytics dashboards to use the... (#542166 - closed)

Screenshots or screen recordings

Before	After
Project dashboard Group dashboard	Project dashboard Group dashboard

How to set up and validate locally

• Go to project/group analytics dashboard and verify that everything works correctly
• (optional) Run storybook and verify that dashboard-related component stories render correctly

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.