Split serialization tests to their own file (#32241)
Summary:
Stacked PRs
* #32244 - Make zip serialization the default
* **#32241 - Split serialization tests to their own file**
This makes them all easier to run as a batch. This PR is just a code move / fixing up imports. There are still some serialization tests in `test_torch.py` as part of `TestDeviceType`.
](https://our.intern.facebook.com/intern/diff/19415826/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/32241
Pulled By: driazati
Differential Revision: D19415826
fbshipit-source-id: a3f6cfe1626ff2f9b9631c409bf525bd32e4639b
