Add cycle metrics to the Analytics exec dashboard

What does this MR do and why?

Issue: #381639 (closed)

Adds new table rows for VSA metrics to the Analytics exec dashboard. These metrics were already included in the existing API requests being made, so I just adding them was as easy as adding them to the constants file.

During testing I noticed that the API returns '-' as a value for empty metrics. I updated generateDoraTimePeriodComparisonTable() to be more robust, since the value formatting helpers were returning NaN in that case.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable the Exec dashboard

   Feature.enable(:group_analytics_dashboards_page)

2. Visit the exec dashboard: http://gdk.test:3000/groups/${YOUR_GROUP}/-/analytics/dashboards

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.