Mark top 3 slowest tests as slow (#46068)
Summary:
`TCPStoreTest.test_numkeys_delkeys` takes 5+ min (mostly in idle wait for socket timeout)
`TestDataLoader.test_proper_exit` and `TestDataLoaderPersistentWorkers.test_proper_exit` take 2.5 min each
`TestXNNPACKConv1dTransformPass.test_conv1d_with_relu_fc` takes 2 min to finish
Add option to skip reporting test classes that run for less than a second to `print_test_stats.py` and speed up `TestTorchDeviceTypeCUDA.test_matmul_45724_cuda`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/46068
Reviewed By: mruberry
Differential Revision: D24208660
Pulled By: malfet
fbshipit-source-id: 780e0d8be4f0cf69ea28de79e423291a1f3349b7
