support renamed symbols in annotation scans

support renamed symbols in annotation scans

Added support in ORM declarative annotations for class names specified for
:func:`_orm.relationship`, as well as the name of the :class:`_orm.Mapped`
symbol itself, to be different names than their direct class name, to
support scenarios such as where :class:`_orm.Mapped` is imported as
``from sqlalchemy.orm import Mapped as M``, or where related class names
are imported with an alternate name in a similar fashion. Additionally, a
target class name given as the lead argument for :func:`_orm.relationship`
will always supersede the name given in the left hand annotation, so that
otherwise un-importable names that also don't match the class name can
still be used in annotations.

Fixes: #8759
Change-Id: I74a00de7e1a45bf62dad50fd385bb75cf343f9f3