[JIT] Add buffer/parameter metadata test to test_save_load.py (#49594)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/49594
**Summary**
This commit adds a unit test to `test_save_load.py` that checks that
saving and loading a module preserves metadata about which module
attributes are parameters and buffers. The hooks that are currently used
to automatically check serialization of every function and module in the
unit tests check that the archive produced by saving and loading and
saving again are the same and that the type tags for the actual IValues
representing the module match before saving and after loading. However,
these tests do not check that buffer and parameter metadata was not
lost or destroyed during serialization.
**Test Plan**
Ran the new unit test.
Test Plan: Imported from OSS
Reviewed By: xw285cornell
Differential Revision: D25730603
Pulled By: SplitInfinity
fbshipit-source-id: 06a202935d9e0654cb1966c34f54707f0a28a331
