feat: add duration_total metrics

[nickpalmer]

We would like to be able to easily see the total pipeline time and total job time for a given period of time.

Unfortunately doing:

sum(increase(gitlab_ci_pipeline_duration_seconds[$(__interval)]))

either touches too much data or runs over the maximum query time for GCP Dashboards.

By adding metrics that track the total job and pipeline times we hope to be able to do the increase query in our environment.

[nickpalmer]

I need to check Gitlab behavior with respect to how it handles a retry of a job in an existing pipeline to make sure that incrementing the total is the correct behavior.