Make use of collection management for updatable entity views in flushing

[beikov]

Currently we only use the collection management features for deletion but query flushing would greatly benefit from it as well since we could avoid loading collections altogether.

[beikov]

Note that we currently flush the entity manager early in ViewCollectionRemoveListener because it is needed to implement orphan removal(#507) properly for collections. Updatable collections currently cause a fallback to entity flushing which will be fixed by the solution for this issue. Don't forget to remove the flushing when implementing this.