Allow custom sorting of column in the ORM.

Allow custom sorting of column in the ORM.

To accommodate a change in column ordering used by ORM Declarative in
SQLAlchemy 2.0, a new parameter :paramref:`_orm.mapped_column.sort_order`
has been added that can be used to control the order of the columns defined
in the table by the ORM, for common use cases such as mixins with primary
key columns that should appear first in tables. The change notes at
:ref:`change_9297` illustrate the default change in ordering behavior
(which is part of all SQLAlchemy 2.0 releases) as well as use of the
:paramref:`_orm.mapped_column.sort_order` to control column ordering when
using mixins and multiple classes (new in 2.0.4).

Fixes: #9297
Change-Id: Ic7163d64efdc0eccb53d6ae0dd89ec83427fb675