PIM-2795: Create factory for job instance

| Q                    | A
| -------------------- | ---
| Bug fix?             | N
| New feature?         | N
| BC breaks?           | N
| CI currently passes? | N
| Tests pass?          | Y
| Scenarios pass?      | Y (no change)
| Checkstyle issues?   | N
| Changelog updated?   | Y
| Fixed tickets        |
| Doc PR               |
why not the %pim_import_export.factory.job_instance.class% ?