suppport with_loader_criteria pickling w/ fixed callable

suppport with_loader_criteria pickling w/ fixed callable

Fixed issue where a :func:`_orm.with_loader_criteria` option could not be
pickled, as is necessary when it is carried along for propagation to lazy
loaders in conjunction with a caching scheme. Currently, the only form that
is supported as picklable is to pass the "where criteria" as a fixed
module-level callable function that produces a SQL expression. An ad-hoc
"lambda" can't be pickled, and a SQL expression object is usually not fully
picklable directly.

Fixes: #8109
Change-Id: I49fe69088b0c7e58a0f22c67d2ea4e33752a5a73