Exec dashboards: expose all flow metrics via GraphQL

This issue is a continuation of #384559 (closed) where one flow metrics is already exposed via GraphQL. In this issue we want to expose the rest of the metrics:

• Deploys
• Lead time
• Cycle time

These metrics are implemented here: https://gitlab.com/gitlab-org/gitlab/-/tree/master/ee/lib/gitlab/analytics/cycle_analytics/summary/

The metrics are currently requested via the SummaryController.

Implementation

group(fullPath: "gitlab-org") {
  valueStream(from: "", to: "") {
    flowMetrics {
       issueCount(milestoneId:, assigneeUsernames: [], milestoneTitle: "", labelName: [], authorUsername: "") { // already implemented
         identifier
         value
         title
         links
         unit
       }
       deploymentCount { // doesn't support any filters except the from, to from valueStream
         identifier
         value
         title
         links // options, array of strings
         unit // optional
       }
       leadTime(milestoneId:, assigneeUsernames: [], milestoneTitle: "", labelName: [], authorUsername: "") {
         identifier
         value
         title
         links
         unit
       }
       cycleTime(milestoneId:, assigneeUsernames: [], milestoneTitle: "", labelName: [], authorUsername: "") {
         identifier
         value
         title
         links
         unit
       }
    }
  }
}