[WIP][PromotionBundle] The collection form type uses the new CollectionExtension

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Behat?    | no and It will use the FormContext in #2218
| Phpspec? | no
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Wrongly placed `)`. Should be:
```diff
- ->addEventSubscriber(new BuildRuleFormListener($this->checkerRegistry, $builder->getFormFactory()), $options['rule_type'])
+ ->addEventSubscriber(new BuildRuleFormListener($this->checkerRegistry, $builder->getFormFactory(), $options['rule_type']))