Make canada use en-US by default if the LI is "en"

Introduce the notion of a fallback mapping to choose a fallback
locale with the same language if an exact match is found. "en-CA"
will fall back to "en-US" under this arrangement. If no fallback
is specified, we continue to arbitrarily choose the first locale
in the list where the language matches.

Also, take the SIM records (EF-LI, EF-PL) into consideration when
matching locales. If we can't find a match based on the sim language,
we fall back to the "likely" language based on ICU data.

bug: 22684963

Change-Id: I8259fd16fc45bbaf2632256cd6f29b46317a5e23