As a precaution, assertQueries() attempted to clone Q() objects

through a deepcopy. This ended up being a bad idea, for two reasons.


Q() handles its own cloning logic already, and is careful about

   it. Mostly because of the second reason.


A naive deepcopy ends up cloning the model instances and their

   fields and other state, which has side effects and is incompatible

   with some types of data (such as the InstanceState objects in

RelationCounterField, due to weakref usage).


We now just use the instances as normal, leaving it up to Q() to do

the right thing.

All unit tests using assertQueries() pass, and in-progress ones that

hit these issues no longer cause Python to crash.