A project can have the same `LfsObject` linked with up to three
`LfsObjectsProject` records. Each of these records would be for a
different repository, recorded in the `repository_type` property. The
different repositories at time of writing are "project", "wiki", and
"design". See https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/13894

This change exports the list of `repository_type`s as a JSON mapping of
oid => repository_types, which are imported to recreate the correct
`LfsObjectsProject` records.

https://gitlab.com/gitlab-org/gitlab-ee/issues/11090