Bug 1032629 - APN Settings UX refresh

https://bugzilla.mozilla.org/show_bug.cgi?id=1032629
Actually I was wondering if it is possible that any apn item is missing here. In https://github.com/mozilla-b2g/gaia/pull/21876/files#diff-f061d3737ee8d3d4d22d4dcfd8f1e28cR557 we save all matched apn items to `ril.data.default.apns`. Note that the value is exactly as what we save to `'ril.data.apnSettings' when building apn settings.