ExpansionServer for the provided ExpansionService running on an arbitrary
port.gRPC Server for an ExpansionService.TransformProvider instances from RunnerApi.FunctionSpecs.ExternalTransformRegistrar.ExpansionService.ExpansionServiceOptions.getJavaClassLookupAllowlistFile(), defaulting to an empty
JavaClassLookupTransformProvider.AllowList.ExpansionServer is bound to.ExpansionServer is bound to.ConfigT from an ExternalTransforms.ExternalConfigurationPayload.RunnerApi.FunctionSpec to a PTransform, together with
mappings of its inputs and outputs to maps of PCollections.TypedSchemaTransformProvider for WindowInto.