PIM-2726 Always indexed value prices by currency

| Q                   | A
| ------------------- | ---
| Bug fix?            | yes
| New feature?        | no
| BC breaks?          | yes
| Tests pass?         | yes
| Scenarios pass?     | yes
| Checkstyle issues?  | no
| Changelog updated?  | no
| Fixed tickets       | PIM-2726
| Doc PR              |