Resolve "Security dashboard empty state"

What does this MR do?

This MR adds the empty state to the security dashboard.

What are the relevant issue numbers?

Closes #7941 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• EE specific content should be in the top level /ee folder