Enable group policy editing

What does this MR do and why?

Enable group policy editing

• create index file for group/policies/edit
• the backend for this is already in place and the frontend mirrors that for the new page

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable :group_level_security_policies feature flag
2. Upload a GitLab Ultimate license
3. Navigate to a group => Security & Compliance => Policies
4. Create a policy and then edit it

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 #345318 (closed)