Avoid executing side-effectful graph_module as validation step (#107271)
Dynamo currently runs the real graph module with real inputs as a way to match the return result of graph module with the eager return type. This is unsafe when graph module is side effectful. In the long term, we will get rid of this step. But in the short term, we just fakify the graph module again and run it.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/107271
Approved by: https://github.com/ezyang
