Validate the Projects::Settings::RepositoryController#show collecting branch counts that it might not need

The following discussion from !74058 (merged) should be addressed:

• @reprazent started a discussion:

  https://log.gprd.gitlab.net/goto/39e6fe9029e7a211a15825d4b4456485

  This endpoint seems to be slow because it's loading all branches and tags from the repository to count how many refs would be protected: https://gitlab.com/gitlab-org/gitlab/blob/636f2ca5ba3769719dc865a01f9445f89fcf0ff9/app/controllers/projects/settings/repository_controller.rb#L83

  The logs confirm this: https://log.gprd.gitlab.net/goto/3d79f6c48e6c74f89dbc505879ad7123

  The cpu_s there seems to be iterating the branches & tags and matching regexes.

  Though the endpoint is not super busy, so we could tolerate this low urgency for now, but what do you think about improving the performance by limiting the number of refs we're matching and display a 99+ kind of value.

  But I think there might be a bug here, we're doing all this counting, for protected branches and tags, but then we're only showing this number (which I think would be 0) if @protected_branches would be empty: https://gitlab.com/gitlab-org/gitlab/blob/636f2ca5ba3769719dc865a01f9445f89fcf0ff9/app/views/projects/protected_branches/shared/_branches_list.html.haml#L4

  Do you think this is worth looking into before we lower the urgency?