Enable corpus management for self-managed installs

MR

Looks like downstream pipelines have been failing for a lot of people:

https://gitlab.com/gitlab-org/gitlab-qa-mirror/-/pipelines?page=5&scope=all

Thoroughly tested in staging and production:

#350974 (closed)

#350975 (closed)

Graphql-verify failure due to a known bug

#352025 (closed)

!79381 (merged)

What does this MR do and why?

Enables corpus management for Self-managed.

Production project for testing:

https://gitlab.com/farias-gl/go-fuzzing-example-with-corpus-management/-/security/configuration

Production testing issue: Corpus Management testing - Production

Roll out issue for backend flag:

#328418 (closed)

Roll out issue for frontend flag:

#349014 (closed)

Docs:

!77430 (merged)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #349014 (closed)