Allow alternative time zone ID to be set device's zone.

If America/Godthab is set as device time zone, display it as if
America/Nuuk is chosen.
If time zone is known, but is not an alternative and not shown
in time zone picker, region will de derived from user's locale.

Bug: 155738410
Test: atest com.android.settings.datetime.timezone.model
Test: set persist.sys.timezone via adb and checked
Date & Time screen

Change-Id: I168fb4319e144dbe9e2496d06a681d4c09b411c0

src/com/android/settings/datetime/timezone/RegionZonePicker.java

@@ -103,7 +103,7 @@ public class RegionZonePicker extends BaseTimeZoneInfoPicker {
         // It could be a timely operations if there are many time zones. A region in time zone data
         // contains a maximum of 29 time zones currently. It may change in the future, but it's
         // unlikely to be changed drastically.
-        return getRegionTimeZoneInfo(filteredCountryTimeZones.getTimeZoneIds());
+        return getRegionTimeZoneInfo(filteredCountryTimeZones.getPreferredTimeZoneIds());
     }
 
     /**