Enable group import be able to import `json` or `ndjson` without flipping the feature flag.
The introduction of the Group Import/Export with ndjson is not backward compatible, which means that after enabling the group_import_export_ndjson
Feature Flag users will be able to use only ndjson
.
To avoid that we need a way to enable the Group Import to be able to import either ndjson
or json
exported packages.
POC: !30055 (merged)