ensure util.get_annotations() is used

ensure util.get_annotations() is used

Fixed issue in Python 3.14 where dataclass transformation would fail when
a mapped class using :class:`.MappedAsDataclass` included a
:func:`.relationship` referencing a class that was not available at
runtime (e.g., within a ``TYPE_CHECKING`` block). This occurred when using
Python 3.14's :pep:`649` deferred annotations feature, which is the
default behavior without a ``from __future__ import annotations``
directive.

Fixes: #12952
Change-Id: I32f0adba00c32f5bf98fe2880dda1b96a7774d07
(cherry picked from commit 03dbd830e174685964191f739ea784f51c97d6b3)