[api test dist] Stubbed out the API for the higher-level `RoutingProxy` object to be exposed by `node-http-proxy`

Not in the "async/fibers/coro" sense of flow control, but in the TCP
backpressure sense.

Pause the stream when a write isn't flushed, and then resume it once the
writable stream drains.

Detach listeners and clean up buffer on error

[test fix] A few minor fixes to ensure basic WebSocket tests are working. Better scope tests by supported protocol