[Testing] Add `--save-xml` option (#37840)
Summary:
Passing `--save-xml` option to common test runner would have the same effect as setting up `IN_CIRCLECI` environment variable, but also would allow one to specify folder to save results
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37840
Differential Revision: D21410250
Pulled By: malfet
fbshipit-source-id: ae5855fafdc8c66b550d42b683d547c88b4e55d9
