symintify nll loss fns (#86915) (#87095)
This reverts commit bbd7b38d5580c44ffb4404d431e07bc2316e59d5.
Reland https://github.com/pytorch/pytorch/pull/86915 with a fix for python arg parser handing for SymInt and SymIntList.
This was uncovered because we are calling directly into python bindings code through test_autocast.py (`torch._C._nn.nll_loss`) without providing a value for the optional symint arg (`ignore_index`). The arg parser constructs the SymInt and SymIntList using the recorded "default_int" or "default_int_list" (schema string parsing) in case a value is not received for an optional argument. Since we weren't handling the symint case properly, the default_int just had a garbage value which was later being used to construct SymInt.
Follow up issue for other unhandled parameter types: https://github.com/pytorch/pytorch/issues/87283
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87095
Approved by: https://github.com/ezyang, https://github.com/albanD
