Check for hybrid's attribute name and support no name

Check for hybrid's attribute name and support no name

Fixed regression where the ORM compilation scheme would assume the function
name of a hybrid property would be the same as the attribute name in such a
way that an ``AttributeError`` would be raised, when it would attempt to
determine the correct name for each element in a result tuple. A similar
issue exists in 1.3 but only impacts the names of tuple rows. The fix here
adds a check that the hybrid's function name is actually present in the
``__dict__`` of the class or its superclasses before assigning this name;
otherwise, the hybrid is considered to be "unnamed" and ORM result tuples
will use the naming scheme of the underlying expression.

Fixes: #6215
Change-Id: I584c0c05efec957f4dcaccf5df371399a57dffe9