[package] Make exporters write to buffer in fbcode (#54303)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/54303
**Summary**
Creating temporary files can cause problem in fbcode. This commit
updates the packaging tests so that exporters write to a memory
buffer when tests run in fbcode.
**Test Plan**
Continuous integration.
Test Plan: Imported from OSS
Reviewed By: suo
Differential Revision: D27180839
Pulled By: SplitInfinity
fbshipit-source-id: 75689d59448de2cd1595ef0ecec69e1bbcf9a96f
