Add a pipeline performance overview at group level
## Problem to solve
As a GitLab Admin/DevOps Developer, I want to see performance of my pipelines over time, so I can identify which are slowing down and fix them before developers complain i'm not doing my job.
## 📝 Background
From the UX scorecard research https://gitlab.com/gitlab-org/gitlab-design/-/issues/1671 we learned that there is not group level summary for pipeline performance available today.
This epic is to brainstorm the ideas for adding a high level pipeline performance summary at group and instance level.
epic