API helpers `find_project_merge_request` and `find_merge_request_with_access` are similar
<!--IssueSummary start-->
<details>
<summary>
Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards.
</summary>
- [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=17004)
</details>
<!--IssueSummary end-->
https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2053 added the latter method but still doesn't make use of `MergeRequestsFinder`, which it probably should, but I'm not sure of the implications of that.
Related: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8724
cc @smcgivern @razer6
issue