ETRecord ser/de handling "None" outputs and more (#3039)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/3039

For the ease of communication, let me assign nicknames to the files related to this diff:
* File A: *caffe2/torch/_export/serde/serialize.py*
* File B: *executorch/exir/serde/serialize.py*
* File C: *executorch/exir/serde/export_serialize.py*

Recently, we noticed that error `torch._export.serde.serialize.SerializeError: Unable to deserialize output node Argument(as_none=[])` (P1210590561) was thrown from File B when deserializing ETRecord. It's possible that the error has been there since the beginning, but we've just never tested that logic path.

In this diff, I made a fix on File B to resolve this particular issue. Also adding handling for "None" output case in sdk logic. ***Keep on reading if you don't think the code changes make sense:***

I explored the history of file changes. In chronological order:
1. D48258552, `deserialize_graph_output()` was copied from File A to File B, with some modifications made. The `deserialize_graph_output()` in File B overrides that in File A due to polymorphism.
2. D52446586, File C was created by ***copying*** File A. As a result of this diff, the `deserialize_graph_output()` in File B now overrides that in File C.
3. Also in D52446586, the `deserialize_graph_output()` in File A had some significant changes; File C got the new version of `deserialize_graph_output()`. But this diff didn't update the `deserialize_graph_output()` in File B.
4. D55391674 added the handling for "None" outputs to File A.

This diff brings (parts of) File C up-to-date with File A, and make `deserialize_graph_output()` in File B properly overrides that in File A.

In the future, we should figure out how to keep File C and File A in sync. Recently, File C was broken because it didn't stay in sync with File A in D54855251 and had to be fixed by D55776877. There will be a design review session this Friday to discuss consolidating the serialization code for edge and export.

Reviewed By: tarun292

Differential Revision: D56091104

fbshipit-source-id: 20c75ddc610c3be7ab2bb62943419d3b8b2be079