Ensure diff patch size limit is monitorable
Per me in https://gitlab.com/gitlab-org/create-stage/issues/41#note_203404933:
An individual diff file in a diff is collapsed based on a configurable "maximum diff patch size"
- Configurable: Yes, in the admin area
- Documentation: Yes, see https://docs.gitlab.com/ee/user/admin_area/diff_limits.html and https://docs.gitlab.com/ee/development/diffs.html#expandable-patches-collapsed
Per &1737, we would like this limit to be configurable and monitorable. I've asked for clarification on what that should look like in &1737 (comment 205413018).