[fx] store Tracer class on Graph and GraphModule for package deserialization [v2, the re-do] (#63121)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63121
Re-introducing this diff with a small change to ignore setting Tracer classes on GraphModules when the Tracer class is defined not at module-level (prevents pickling).
Previous, reverted Pull Request: https://github.com/pytorch/pytorch/pull/62497
Reviewed By: houseroad
Differential Revision: D30252776
fbshipit-source-id: 42d2bc846e4b32d00563419c38c02b63cd0986e6
