Fix Japanese Chronology.

The JapaneseChronology class depends on the ImperialJapaneseCalendar
being returned by Calendard.getInstance(). Since Android always returns
a GregorianCalendar from that class, the tests will fail.

This fixes the problem by importing the JapaneseImperialCalendar class
from the OpenJDK (with minor tweaks to remove mentions of the ZoneInfo
class) and adapting the relevant classes to use a new explicit method on
Calendar to request such a calendar instance.

Also apply update LocaleGregorianCalendar to jdk8u60 which fixes an
off-by-one error in calculations related to eras.

Added ChronologyDisplayNameTest to ensure future Chronologies return
sane values for their display name and their eras display names.

Bug: 28832222
Test: artrun testng-time.xml
Test: run cts -m CtsLibcoreTestCases
Change-Id: I3eb5d4509ad03ee3d736c7926c605f378b56d0b2