V2 Executions Pipeline Self-Host Telemetry: Step completion statistics

[evolutionise]

See parent issue for details.

This issue covers adding telemetry for step completion statistics for deployment/runbook server tasks, and full server task duration

[octoreleasebot]

Release Note: Added step/deployment completion statistic telemetry for self-hosted customers

[Octobob]

🎉 The fix for this issue has been released in:

Release stream	Release
2025.3	2025.3.14655
2025.4	2025.4.10306
2026.1	2026.1.3842