[Feature Request]: Read Kafka Producer topic from field

### What would you like to happen?

migration: https://issues.apache.org/jira/browse/HOP-4147

It would be awesome to read the topic a row is sent to from a field.

This would enable more fine-grained control over the routing and probably save a lot of Kafka Producer nodes.

### Issue Priority

Priority: 3

### Issue Component

Component: Transforms

Start by locating the Kafka Producer transform mentioned in the issue and review migration HOP-4147. Determine how the producer currently selects its topic, then verify that a row field can control routing and that the behavior reduces the need for separate Kafka Producer nodes.

Written by the indexing model from the issue text.