Allow Transformer accept output result that is not Proxy (#52473)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52473
Use `map_aggregate` to create output for new graph so that it won't raise error when we have outputs that is not `Proxy`.
Test Plan: `test_transformer_multi_outputs` in `test_fx.py`
Reviewed By: jamesr66a
Differential Revision: D26502277
fbshipit-source-id: 404d9030a9b84db3f66f8505887a75717a28ad30
