remove ui blueprints from API entrypoints

[fenekku]

This invenio_requests_ui = invenio_requests.views:create_ui_blueprint in setup.cfg under api_blueprint should, apriori, not be necessary for a real system. We should remove it to clean up the system and make things clear.

However tests will fail because notification tests and notification generating tests are under API app and attempt to use email templates which a real system would have done by worker app. There may be more investigation needed here + possibility for a rabbithole...