Rename remote mirrors and mirrors to push and pull mirrors
<!--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=24307) </details> <!--IssueSummary end--> I've brought this up in https://gitlab.com/gitlab-org/gitlab-ee/issues/2954 before. In reading and reviewing code, I frequently get mixed up with our terminology of "remote mirrors" and "mirrors". Most recently we introduced a bug because of this mixup (https://gitlab.com/gitlab-org/gitlab-ce/issues/51725). @DouweM argues this isn't the right term in https://gitlab.com/gitlab-org/gitlab-ee/issues/2954#note_35847814, but I've seen that the community generally understands "pull" and "push" mirror quite well (e.g. https://gitlab.com/gitlab-org/gitlab-ce/issues/18732#note_96811837). /cc: @jramsay
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