Add env var PYTORCH_TEST_RUN_EVERYTHING_IN_SERIAL=1 that allows running unit test suites in serial (#90981)
Running unit test suites in parallel sometimes creates unexpected errors. This PR adds an option that allows unit test suites to be executed in serial, by setting PYTORCH_TEST_RUN_EVERYTHING_IN_SERIAL=1.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/90981
Approved by: https://github.com/malfet, https://github.com/ptrblck
