We see `test_extension_store_with_test_extension` hang in untarring the WASI SDK some times. In lieu of trying to debug the problem, let's try shelling out for now in the hope that the test becomes more reliable. There's a bit of risk here because we're using async-tar for other things (but probably not 300Mb tar files...) Assisted-By: Zed AI Closes #ISSUE Release Notes: - N/A