PIM-2515: deleting completeness when a locale of a channel is deleted

| Q                   | A
| ------------------- | ---
| Bug fix?            | Y
| New feature?        | N
| BC breaks?          | Y
| Tests pass?         | Y
| Scenarios pass?     | N
| Checkstyle issues?  | N
| Changelog updated?  | Y
| Fixed tickets       | PIM-2515
| Doc PR              | -

The best solution would have been to create a ScheduleCompletenessSubscriber but it's impossible due to circular dependencies. The deletion is done in the ChannelHandler via the CompletenessManager.

Two Doctrine registry dependencies have also been replaced by the proper services.