Add integration hooks for WebDriver-BiDi

[jgraham]

WebDriver wants a hook that's called for every console API call, so that it can emit a relevant message; see w3c/webdriver-bidi#73

The current spec draft defines the following patch:

## Console ##  {#patches-console}

The [=Printer=] operation is modified with a single required step before the
implementation defined behaviour:

1. Call any <dfn>console Printer steps</dfn> defined in external specification
   with arguments <var ignore>logLevel</var>, <var ignore>args</var> and,
   <var ignore>options</var> if the <var ignore>options</var> object was
   passed, or undefined otherwise.

Although this isn't quite right, since some operations don't go through the Printer method (e.g. grouping operations).

[terinjokes]

The Console specification deliberately under specifies what implementations do with calls to most API methods, to allow implementations large flexibility in surfacing this information to developers (eg, in a GUI, terminal messages, web page viewing the status of a remote agent, etc).

Agents are already free to define hooks and be compliant with this specification. Is there a need for such functionality to be defined here?

[jgraham]

It's not about agents as such, it's about how another spec should hook into "a method on the console object is called" and get the method name and the arguments (post-formatting).

[domfarolino]

This seems pretty reasonable. @jgraham are there any plans on porting over some of the WebDeriver BiDi spec to a PR over here?