Fixes memory leak on generic Doctrine Writer

The writer uses now the ProductCacheClearer
| Q                    | A
| -------------------- | ---
| Bug fix?             | Yes
| New feature?         | No
| BC breaks?           | Yes
| CI currently passes? | Yes
| Tests pass?          |  Yes
| Scenarios pass?      | WIP
| Checkstyle issues?*  | No
| PMD issues?**        | No
| Changelog updated?   | Yes
| Fixed tickets        | PIM-3121
| Doc PR               |