Run the ROR funders update as a Celery task

[ptamarit]

Depending on the following pending changes:

• Another earlier pull request: inveniosoftware/invenio-app-rdm#2674
• The pull requets linked to this issue: #331

Then on an InvenioRDM instance, start InvenioRDM without celery:

invenio-cli run -n

On another terminal in the InvenioRDM instance, start celery:

invenio-cli shell
celery -A invenio_app.celery worker --loglevel=DEBUG -Q celery

And on another terminal, trigger the task:

invenio-cli shell
invenio shell

from invenio_vocabularies.services.tasks import import_funders
import_funders.delay()

[ptamarit]

• [x] Do inserts only for now (this way, there is no need to reindex dependent entities like communities).
• [x] Download the ROR file for the Celery task without breaking the existing CLI functionality with a local file.