[sgen] Fix critical/normal finalization order at domain unload

[sgen] Fix critical/normal finalization order at domain unload

For objects that die at the same time, normal finalizers should be run before critical finalizers. When we were unloading a domain we were running finalizers for all objects in that domain without checking whether the finalizer is critical or not. Now we enqueue the objects first in the finalization queues so we can run all the normal finalizers before the critical ones.