Ensure "global" resources can be deallocated

[tgolsson]

Currently multiple of the trampoline parts are never deallocated, assuming that they'll live forever. This includes the new ErrorCallback, the ProfilerCallback, and potentially others. Since PhysX takes ownership of these but doesn't delete them, we have to keep the pointers around and delete them manually when the foundation is dropped, or return a collection of pointers for the user to deal with it.