Implement TransformStream cleanup using "transformer.cancel"

[lucacasonato]

The Streams specification has been updated with support for a hook to cleanup a TransformStream on error / abort. See whatwg/streams#1283. WPTs are available: web-platform-tests/wpt#40453

[debadree25]

I am trying to implement this, i am coming across some weird behaviour for the test https://github.com/web-platform-tests/wpt/blob/1267d50de7f8adf06dbddaba00b4d9651ae146a4/streams/transform-streams/errors.any.js#L266 it seems after calling controller.error the writable stream should also error? if so cancelPromise should also throw because writable has entered errored state? or is node's behaviour wrong here?