Add tests for custom state_dict save/load methods in TorchScript (#57886)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/57886
Reviewed By: jamesr66a
Differential Revision: D28309228
Pulled By: gmagogsfm
fbshipit-source-id: 6ac60b1d4a8017aefb6f6dff49cde598de000265
