GitLab

1. Move misplaced sox compatibility test (T,Fade, T.Vol, T.Vad) to test/test_sox_compatibility.py
2. Move test_sox_effects to test/sox_effect/ where all the other functionalities from torchaudio.sox_effects are tested

Currently all the tests in `sox_io_backend` and `sox_effects` (for new SoX effects implementation) requires additional `sox`, and this prevents running test in environment where `sox` command is not available even though `torchaudio` extension is available (such as fb internal). This PR adds smoke tests for these modules, which just runs functions to see if they do not crash.

* Add sox_utils module

* Make init/shutdown thread safe

* Add sox effects implementation

* Add test for sox effects

* Update docstrings and add examples