Changes to Get tool catalog

added the new upstream_unavailable enum value to the code response property for the response status 401

added the new upstream_unavailable enum value to the code response property for the response status 403

added the new upstream_unavailable enum value to the code response property for the response status 4XX

added the new upstream_unavailable enum value to the code response property for the response status 503

removed the upstream_error enum value from the code response property for the response status 401

removed the upstream_error enum value from the code response property for the response status 403

removed the upstream_error enum value from the code response property for the response status 503

removed the upstream_error enum value from the code response property for the response status 5XX

added the optional property built_in_tools/items/implicit to the response with the 200 status

endpoint added