check if /splits-name-from-* exists before processing it 
Closes https://github.com/huggingface/datasets-server/issues/963

Adding validation on split names - config level job runners to throw an error if the response of the same info has already been computed.
check if /splits-name-from-* exists before processing it : Closes https://github.com/huggingface/datasets-server/issues/963

Adding validation on split names - config level job runners to throw an error if the response of the same info has already been computed.