test: enable idlharness tests for encoding
TextDecoderStream and TextEncoderStream are now exposed as globals, so we can run the entire Encoding idlharness test suite.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
TextDecoderStream and TextEncoderStream are now exposed as globals, so we can run the entire Encoding idlharness test suite.