Add a getConfigurationFields in ProductReaderInterface

| Q                    | A
| -------------------- | ---
| Bug fix?             | n
| New feature?         | n
| BC breaks?           | y
| CI currently passes? |
| Tests pass?          | y
| Scenarios pass?      | 
| Checkstyle issues?*  | n
| PMD issues?**        | n
| Changelog updated?   | y
| Fixed tickets        | PIM-3400
| DB schema updated?   | n
| Migration script?    | n
| Doc PR               | n