Truncate related merge requests list in pipeline view

Issue: #35378 (closed)

What does this MR do?

Addresses an issue that came up after we added the list of related merge requests to the pipeline view (see #26909 (comment 237484856) for details)

• Truncates the 3 related merge requests: !1 Change some stuff, !2 Change some other stuff, !3 Add a feature text to 3 related merge requests: !1 Change some stuff
• Adds a clickable ellipsis that shows the full list of related merge requests (the full list is what currently shows by default)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers