* Downgraded skips in tests
* Fixed failing tests
* Fixed test_ftplib + test_socket + test_ssl + test_threaded_import failures
* Removed comments about which tests are run in which environment
* Addressed PR comments
* Annotated skips on failing tests
* Removed unneeded tests
* Removed unneeded sys import from test_ftplib
* Added annotation to test_ftplib
* Readded skipIf to test_cleanup_with_symlink_modes with a more general ENV_POLLUTING_TESTS_WINDOWS
* Addressed PR comments
* Made changes to minimize diff in PR
* Apply suggestion from @youknowone
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Co-authored-by: Jeong, YunWon <69878+youknowone@users.noreply.github.com>
Initially this is only meant to be a small update for `test_io.py`.
But it turns out that `test.support` need a lot of cleanup especially
for `test.support.warnings_helper`.
Terry Tianlin Luan