Allow Arkose settings to be configured via API

What does this MR do and why?

Related to: https://gitlab.com/gitlab-org/modelops/anti-abuse/team-tasks/-/issues/650

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Ensure GDK is configured to simulate saas

The following attributes should be able to be read/set via the API

arkose_labs_client_secret
arkose_labs_client_xid
arkose_labs_namespace
arkose_labs_private_api_key
arkose_labs_public_api_key