Websocket streaming not cleaned up

[jyu00]

Interim result and job status streaming was removed a while ago. However, a bunch of dead code was not cleaned up, for example:

• There is still code to create the websocket client
• There are several streaming related methods such as cancel_result_streaming
• Also code to establish interim result decoder
• And code to allow user callback

I don't think a ws stream is actually established anywhere, but it's hard to tell because of all the residual code.