Add new setting to Application Settings: receive_max_input_size

What does this MR do?

It adds a new application setting: receive_max_input_size

If the user has entered a value for this setting then this setting is passed in the API response to gitlab-shell and gitlab-workhorse

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Sending large pushes to a GitLab instance is consuming a lot of resources and finally crashing the server.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conforms to the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #26044 (closed)

EE conflicts solved on https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/6812