Related merge requests in pipeline view should be truncated

Summary

Recently, we merged these two MRs to add links to all of the related merge requests to the pipeline view:

• !17947 (merged) (backend)
• !18697 (merged) (frontend)

But when there are many related merge requests, the list becomes cumbersome:

Steps to reproduce

Run a pipeline for a commit that is related to more than one merge request

Possible fixes

It has been proposed in the original feature issue discussion that we copy the behavior of the commit row that occurs just above this row in the UI:

1. Show a shorter version of the information by default
2. Add an ellipsis to indicate that there is more information available
3. When the ellipsis is clicked, show the full version of the information