Make merge request commits go through Gitaly
What does this MR do and why?
This MR changes the committers field in the Merge Request GraphQL type to use Gitaly instead of relying solely on the database. This is mostly for performance in issues in large MRs and was discussed here: https://gitlab.com/gitlab-org/gitlab/-/work_items/579991#note_2929060898
References
Edited by Gary Holtz