Move download CSV functionality to dropdown in metrics

What does this MR do?

Moves the Download CSV functionality into a dropdown:

CSV results: chart_metrics_2_.csv

With the additionalPanelTypesEnabled feature flag:

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Closes #64950 (closed)