As the phantomjs project was suspended[1], there was a need to change the js test
engine. Moreover, the engine was rather old and leading to non
deterministic crashes.

Chrome headless was choosen for simplicity and the long term vision of
the devtools protocol [2].

The 'phantom_js' method still exists but will be deprecated in
favor of 'browser_js' with the same parameters.

In order to communicate with the browser, the python websocket-client package
is needed.

[1] https://github.com/ariya/phantomjs/issues/15344
[2] https://chromedevtools.github.io/devtools-protocol/

#closes 25991

With this commit, we add a few extra logs to help debugging issues with
phantomjs.

I suspect that the recent problems with phantomjs are due to the
localstorage not being cleared properly, but the logs are not sufficient
to determine the exact cause.