Introduce read_admin_groups and read_admin_projects custom admin role permissions

What does this MR do and why?

Introduce read_admin_groups and read_admin_projects custom admin role permissions to grant read-only access to groups and projects pages in the admin area.

References

Part of Permission to view custom attributes (or groups... (#534449 - closed).

Screenshots or screen recordings

How to set up and validate locally

1. Enable custom_roles feature flag.
2. Login with an admin and go to http://localhost:9393/admin/application_settings/roles_and_permissions/
3. Verify that you can create a custom admin role with View Groups and View Projects permissions

MR acceptance checklist

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