Move retried_request from the toolbox

teklia_toolbox.retried_request calls ArkindexClient.request with an added tenacity retry. We can implement it directly in the API client so that consumers need not to depend on both the API client and the toolbox to get this method, and to encourage a more consistent way of retrying across all projects. This more importantly means that the toolbox does not try to fetch the Arkindex API schema when imported, so it can also work without internet access.