Add frontend for user registration restrictions

What does this MR do and why?

What

Add frontend for user registration restrictions

• Page will automatically redirect after 30s (location TBD)
• Buttons to navigate to JiHu specifics

Why

Backend work was done in Prevent new user registration based on geo-IP data (!147697 - merged) • Ian Anderson • 16.11, this adds the UI to correspond

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

FF Enabled	FF Disabled

How to set up and validate locally

1. Enable feature flag (Feature.enable(:prevent_registration_from_china))
2. Visit http://gdk.test:3000/users/identity_verification/restricted

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/442204