Remove time_zones_by_country.xml file

time_zones_by_country.xml has been replaced by a file that can
be updated outside of an OTA and can be accessed via
libcore.util.TimeZoneFinder. This means parsing code has been
removed from this class and replaced by calls to libcore code.

libcore code uses ICU so this class adapts to
java.util.TimeZone for published public APIs as well as other
knock-ons to reduce impact of this change in telephony code.
All use of classes called TimeZone are fully-qualified to
reduce confusion.

Several public-but-hidden methods have been removed. These
can be returned if there are any important apps relying on
them.

Bug: 25338903
Test: Ran CtsUtilTestCases
Change-Id: I699b4e7420e8d7e61ee68ec96552ab3144c9bab2