Use /json/version to retrieve ws url

[ankur22]

Could we use <ip>:<port>/json/version to retrieve the websocket url instead of relying on parsing stdout to retrieve the websocket url? The trouble with using the json endpoint is that we will need to pick and assign the port when launching the browser instance instead of allowing the browser to find an open port, which is an extra moving part in xk6-browser.

[tmc]

This would be nice to support with connect() as well -> allow it to auto-discover.

[inancgumus]

Which IP and port can we connect to without knowing the WebSocket URL firsthand?

I looked into this, and we can use the --remote-debugging-address and --remote-debugging-port flags. However, once we set these to constant values, users won't be able to test with multiple k6 processes, hence the single address and port.