Add shared dashboard layout component

What does this MR do and why?

Adds a new DashboardLayout component in /vue_shared for Add a reusable dashboard layout component (#541899 - closed) that:

• Renders a dashboard with a title, description, filters, alert, panels and empty state.
• Handles the layout of all of the above so that consumers can easily create a dashboard layout.
• Renders the panels inside of GridstackWrapper using a configuration object.
• Empowers consumers to edit the contents within the layout.

This will be used by groupsecurity insights for Implement dashboard layout framework enabling s... (&17819 - closed).

Follow-ups include:

• Updating cutomizable_dashboard.vue to use this component.

References

Add a reusable dashboard layout component (#541899 - closed).

Screenshots or screen recordings

How to set up and validate locally

• Run yarn storybook:start and view the dashboard layout story.

MR acceptance checklist

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