Cycle Analytics: Events per stage

Adds list of events to each stage:

• Issue: list of issues created in the last XX days, that have been labeled or added to a milestone.
• Plan: list of commits that reference for the fist time an issue from the last stage.
• Code: list of MR created in this stage
• Test: List of unique builds triggered by the commits.
• Review: List of MR merged
• Staging: List of deployed builds
• Production: list of issues with the time from idea to production

Fixes #23449 (closed)

• CHANGELOG entry added
• Documentation created/updated
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together