Rely upon Target domain instead of the json/list for page discovery and engagement

[pavelfeldman]

It is preferred to establish a single connection to the browser endpoint over the ws://host:port/devtools/browser/<guid>. That guid can be obtained from the http://localhost:9222/json/version, in the webSocketDebuggerUrl field.

Information about the targets is available over Target.getTargets. One can receive dynamic notifications about the new targets, create and delete targets over that domain.