Add `--repeat` option to python unit-test (#37281)
Summary:
This would run same testsuite (or individual test) multiple time
Useful for detecting flaky tests
Example usage: `python test_autograd.py TestAutograd.test_profiler -v --repeat=100`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37281
Differential Revision: D21244442
Pulled By: malfet
fbshipit-source-id: 3ecafec7ae87bc1e418aa28151bbc472ef37a713
