Description
When using CallStep, providers require access to the serviceName and the merged params from CallStep for implementation.
service name is currently private https://github.com/apache/tinkerpop/blob/master/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/CallStep.java#L63 and merged params getter is protected https://github.com/apache/tinkerpop/blob/master/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/CallStep.java#L195