Fix URLs in user_auto_banned_email

What does this MR do and why?

Resolves https://gitlab.com/gitlab-org/modelops/anti-abuse/team-tasks/-/issues/46.

This MR updates the user_auto_banned email to have the correct URLs to pages where:

• the admin can unban banned users
• the admin can update settings for auto-banning

The URLs depend on whether the user is banned from an instance or from a namespace.

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Files are also moved under ee/ since the email is sent by features that are EE-only.

Screenshots or screen recordings

When user is banned from an instance

before	after

When user is banned from a namespace

before	after

How to set up and validate locally

When user is banned from an instance

1. Go to localhost:3000/rails/mailers/notify/user_auto_banned_instance_email.html?locale=en
2. Hover on here and validate that the URL ends in /admin/application_settings/reporting

When user is banned from a namespace

1. Go to localhost:3000/rails/mailers/notify/user_auto_banned_namespace_email.html?locale=en
2. Hover on unban them and validate that the URL ends in /groups/<group-name>/-/group_members?tabbed=banned
3. Hover on here and validate that the URL ends in /groups/<group-name>/-/settings/reporting

MR acceptance checklist

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