[LTC] Upstream LazyTensor and LazyGraphExecutor (#69815)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/69815
Test Plan: Imported from OSS
Reviewed By: dagitses, jbschlosser
Differential Revision: D33059774
Pulled By: desertfire
fbshipit-source-id: dd1e3e5f4fd3181517eebd2742f6a5b7b6fb9a7d
