[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).
Yeah, if the above felt like too much, I was going to suggest `data-` attributes. That might be a nice compromise.

A big chunk of HTML isn't very developer friendly for getting an overview of and/or editing/augmenting the data. This will only get worse as the number of providers & countries increase. Doesn't mean we need to go server side right now, but something to consider.

If we stick with CSS selector matching, should probably drop the `div` from `'div.provider.' + COUNTRY_CODE`. :smiley: