Catch all retrieval request failures into kgforge.core.commons.exception.RetrievalError

When a request is successful and a response is obtained, when the status code is not within a range (indicating a successful response), a kgforge.core.commons.exception.RetrievalError is raised.

However when the request is not successful (ex: doesn't reach server), another exception is thrown (ex: aiohttp.client_exceptions.ClientConnectorError) see https://bbpgitlab.epfl.ch/dke/apps/brain-modeling-ontology/-/jobs/1342198

Maybe this should be caught and raised as a RetrievalError as well.

This improvement can also generalize to all usage of aiohttp in forge (appropriate exceptions will be raised each time)