Show pipeline, reviewers and other row details in search

What does this MR do and why?

This merge request adds the merge status warning, milestone, discussion count, upvote and downvote counts, pipeline status icon and reviewer avatars to each row of the search list.

The fields already come from the shared merge request fragment, so the GraphQL query is unchanged.

References

Split from !252201 (closed)

Part of a stack:

1. !252305 (merged) - feature flag and backend enablement
2. !252306 (merged) - Vue search list
3. !252307 (merged) - remaining filter tokens
4. !252308 (merged) - (this merge request) row details
5. !252309 (merged) - approval status

Screenshots or screen recordings

Before	After

MR acceptance checklist

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