EntityReference processor uses wrong field name to write data to entity

Problem/Motivation

The EntityReference processor writes the value for a reference field based on the entities it has imported:

        $processed_entity->set($field_public_name, $field_values);

However, $field_public_name is the name for the field in the JSONAPI data:

      foreach ($entity_json_data['relationships'] as $field_public_name => $field_data) {

This should use $field_internal_name name instead.

It's working ok because in most cases, the field name is the same.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes