Allow pytrees as output for make_traced and nvfuser executor (#78802)
This PR lifts the restriction that the output of a function traced with `make_traced` and executed with nvFuser must be a single tensor. Now it's possible to return a "pytree", a tensor's nested data structure (see https://github.com/pytorch/pytorch/blob/master/torch/utils/_pytree.py).
I added a test with a function that returns a tuple of two objects where one of the objects is a dictionary with a tensor value.
```py
def fn(a, b):
d = {}
d["c"] = torch.add(a, b)
return (d, torch.add(a, d["c"]))
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/78802
Approved by: https://github.com/mruberry
