REST export views now support translated entities

While this is a straight bugfix, it's possible that some sites are relying on this broken behavior. Hence this change record.

Assume this scenario:

1. Site with Content Translation enabled. English and French are enabled.
2. Site with REST export views using the Entity row handler
3. Create an entity with the name "Cat". Translate it to French: "Chat".

Then, request a response from the REST export endpoint and notice how:

Drupal 8.1.1 and earlier

… you only see the default site language: "Cat" appears twice, instead of once "Cat", once "Chat".

Drupal 8.1.2 and later

… you see once "Cat", once "Chat".