[BE] Split pytorch_linux_test into 3 steps (#37808)
Summary:
First one is to download build artifacts
Second is to run tests
Third is to upload test metadata (runs always, even if `Run` step has failed)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37808
Differential Revision: D21398398
Pulled By: malfet
fbshipit-source-id: da23c499a84136e12e88adcc60206ea26bc843c9
