Follow-up from "Fix Possible asciidoctor include:: directive DOS"

Everyone can contribute. Help move this issue forward while earning points, leveling up and collecting rewards.

• Close this issue

This is a follow-up issue to move MAX_INCLUDE_DEPTH into an application setting and also change the default for ::Gitlab::CurrentSettings.asciidoc_max_includes:

https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/4298#note_2013892353