Json: in migrations, improve the order in which we generate json columns in the table

Currently we scaffold non-json columns (respecting their order) and then we scaffold all json columns in alphabetical order. Ideally we would put json column in the position that the navigation it's containing is placed in the entity, e.g.

```cs
public class Customer
{
public int Id {get;set;}
public Address WorkAddress {get;set;} // mapped to json
public Address HomeAddress {get;set;} // mapped to json
public string Name {get;set;}
}
```

we should create columns in this order:
```Id, WorkAddress, HomeAddress, Name```

but currently we create:
```Id, Name, HomeAddress, WorkAddress```