Collapse cherry-picked commit references in a MR
At the moment we show the references to a commit in an MR description like this:
Example with many references: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3305#note_47407909
We should be able to collapse that as we do with pushes with a high number of commits, as @winh suggested in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3305#note_47446579.