[dynamo] Record nn_module_stack also for unspecialized nn modules. (#108281)
Summary: Currently node metadata "nn_module_stack" is only being used by export. For some export model, we still want to retain nn_module_stack for unspecialized module for various purposes. This diff add a path to also record nn_module_stack when unspecialized module has a source available.
Test Plan: test_export_nn_module_stack_patched_module
Differential Revision: D48841193
Pull Request resolved: https://github.com/pytorch/pytorch/pull/108281
Approved by: https://github.com/yanboliang, https://github.com/tugsbayasgalan
