Improve time zone detection by leveraging MNC info

Improve time zone detection by leveraging MNC information:
TelephonyLookup in libcore provides information about networks known to
operate in countries other than the one implied by the MCC.

This change only modifies time zone detection behavior: it may not be
appropriate to switch all cases.

Bug: 143451294
Bug: 117863016
Test: atest MccTableTest
Test: atest LocaleTrackerTest
Test: treehugger
Change-Id: I734d699befd355a8f21a13edf922de5b995bbc5b