Add types to _dynamo/testing.py (#136402)
Summary:
X-link: https://github.com/pytorch/pytorch/pull/136402
Approved by: https://github.com/jansel
Reviewed By: atalman
Differential Revision: D63319829
Pulled By: bobrenjc93
fbshipit-source-id: c343ada52068d5d973757093c255726684fb6f70
