Migrate Badges with the Group

Problem to solve

For the Group Migration to be a viable solution for the users migrating Groups, we need to achieve parity with the Group Export/Import feature.

Proposed Solution

Following the implementation of the issue to expose Group Badges in GraphQL, this issue adds Badges to Group Migration.

Documentation

Following documentation should be updated with the fields added in this issue:

• User docs: https://docs.gitlab.com/ee/user/group/import/
• Dev docs: https://docs.gitlab.com/ee/development/bulk_import.html