Fixed #23822 -- Added support for serializing model managers in migration

Ticket: https://code.djangoproject.com/ticket/23822

- [x] Implementation
- [x] User documentation
- [x] Reference documentation
- [x] Tests
You have to inherit since `from_queryset()` generates a class named `MyManagerFromMyQuerySet` (in case of a manager class named `MyManager`) and the serialization working on class not instance level.