[fix bug 1054956] Refactor Firefox OS Get phone logic to remove JS dependency

Refactored "Get a Phone" logic on `/firefox/os/` and `/firefox/os/devices`, so users with JS disabled will get a full list of available phone partners/links in all countries (instead of just a link to the FAQ page). This should mean we now also have just a single list to maintain (in plain HTML :+1:). This will unblock [bug 1049042](https://bugzilla.mozilla.org/show_bug.cgi?id=1049042).

P.S - I also cleaned up some indentation in `get_devices.less` (adding `?w=1` to the PR URL might make review of this file easier).
With JS disabled, some countries have missing (Germany) or incorrect (Hungary/T-Mobile) logos. Maybe use the `data-country` attribute in CSS? That would save us from having to add the `COUNTRY_CODE` as a class name.