Support default_factory=list for write only / dynamic relationships

Support default_factory=list for write only / dynamic relationships

Fixed regression caused by the dataclasses change in :ticket:`12168`
where passing :paramref:`_orm.relationship.default_factory` as ``list``
to a relationship that used the :class:`_orm.WriteOnlyMapped` or
:class:`_orm.DynamicMapped` annotation would raise an error at mapper
configuration time, as these relationships have no ``collection_class``.
``list`` is now accepted for these relationships, which behave the same
as ordinary collections in this regard; the factory itself is never
invoked, and a newly constructed object begins with an empty
collection.  Documentation is added at :ref:`write_only_dataclasses`
illustrating the use of write only and dynamic relationships with ORM
mapped dataclasses.

Fixes: #13227
Change-Id: I809b408b0eabf0235f9d6e95871a85eba3917e61