Clarify what exactly are excluded for calculating pipeline duration

What does this MR do and why?

Clarify what exactly are excluded for calculating pipeline duration

It means all the jobs which had been retried will be excluded, and the new jobs created by retrying will be counted instead.

The confusion can be observed in https://gitlab.com/gitlab-org/quality/engineering-productivity/team/-/issues/378#note_1739971254

At least in my view, retried jobs should not be included in the calculation. My take is that we only want to optimize the first successful run of a pipeline. This is partially done in the product (we don't include retried jobs in the pipeline duration) 🎉

It is not clear what are retried jobs.

See #439372 (closed)