Pickling fixes for ORM / Core

Pickling fixes for ORM / Core

Fixed regression where ORM loaded objects could not be pickled in cases
where loader options making use of ``"*"`` were used in certain
combinations, such as combining the :func:`_orm.joinedload` loader strategy
with ``raiseload('*')`` of sub-elements.

Fixes: #7134
Fixed issue where SQL queries using the
:meth:`_functions.FunctionElement.within_group` construct could not be
pickled, typically when using the ``sqlalchemy.ext.serializer`` extension
but also for general generic pickling.

Fixes: #6520
Change-Id: Ib73fd49c875e6da9898493c190f610e68b88ec72