__reduce__ for QScheme (#24969)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/24969
This allows pickling qscheme objects
Test Plan: Imported from OSS
Differential Revision: D16946567
Pulled By: jamesr66a
fbshipit-source-id: 57dbedb1e1aca2a2e17916eed662f727053ea926
