This is the first part of a bigger patch to make WebConsoleFront methods
consumers handle fronts instead of plain grips.
The main challenge with most of console methods is that the server
can return either a primitive, an object that represent a primitive
(undefined, null, Infinity, ...), a longString grip or an object grip.
Since this would be complex to map as a protocol.js type, this patch
either override the methods where we want to return fronts, or intercept
events with the `before` method on them.
The response is then handled to a function that will iteratore of the
result object in a recursive manner, and create fronts when needed.
Differential Revision: https://phabricator.services.mozilla.com/D54506