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
Not yet, but it relates to [#23861](https://code.djangoproject.com/ticket/23861), [#23891](https://code.djangoproject.com/ticket/23891) and [#23892](https://code.djangoproject.com/ticket/23892)