Review project import/export ramifications for work item types

We need to determine the exact requirements for exporting work item types, the work_item_types table and the issue.work_item_type_id.

When exporting a project, should the work item type of an issue be exported/imported? We would need to recreate the same work item types that the issues refer to.

See lib/gitlab/import_export/project/import_export.yml and spec/lib/gitlab/import_export/all_models.yml

Currently we're not exporting the table or work_item_type_id