Stop hardcoding carrier for some regions (bug 1061716)

https://bugzilla.mozilla.org/show_bug.cgi?id=1061716

This was introduced in 2f67a82 to be more more DRY, but it was wrong in some cases: for instance, it meant your carrier was automatically set to 'deutsche_telekom' if you had an US SIM.

Also took the time to sort the 2 arrays by MCC.
Unsure of what to test. I wanted to test that the number of keys in `regions` and `carrierRegions` is the same, if we add Austria, Paraguay and Slovakia to `regions` then I could do that (only works in one direction, cause there are some regions for which we don't have carriers defined, like France - because we launched without a carrier partner there).

If you have any other suggestions I'll gladly add more.