Use the shallowest path when an object is loaded at multiple paths

Use the shallowest path when an object is loaded at multiple paths

Fixed long-standing issue where an object that was loaded at more than
one path within a single query, such as when a chain of joinedload()
options leads back to an entity that was also loaded at the top level of
the query, would retain the loader options of whichever path the query
happened to see last, which varied with the loader strategy in use.  The
options an object retains are applied to all forms of lazy loading for
that object, so an otherwise identical set of options could behave
differently depending on the loader strategy.  The shallowest path is
now favored, which is deterministic.

Fixes: #13507
Change-Id: I438e6655a9ecf59ca554312a7a87c8b85b4879d2