Refactor QueryConnection

Problem/Motivation

The QueryConnection class is a good candidate for refactoring. I am extending this class to customize translation fallback behavior for a client project and I am running into a number of gotchas:

1. The class doesn't have an interface.
2. The class is instantiated directly, which means in order to invoke it I also need to extend its parent classes. It would be easier if this is a service which can be swapped out.
3. The ::getResolveCallback() method is private. I cannot call it from a subclass and need to copy it into my own code.
4. There are three services being sideloaded through the \Drupal facade, these can be injected.