Switch DateIntervalFormat/RelativeDateTimeFormatter to ICU4J

Information below from the existing benchmarks on a hammerhead. All
times given in microseconds. Note that the new version is slower,
but this is a small difference in absolute terms and means less
maintenance for libcore.

The ICU team is rewriting some of the underlying code in ICU4J
for a future ICU release which may alter performance.

ICU4C + JNI
DateIntervalFormat_formatDateRange_DATE 67.8
DateIntervalFormat_formatDateRange_DATE_TIME 76.0
DateIntervalFormat_formatDateRange_TIME 54.8
ICU4J
DateIntervalFormat_formatDateRange_DATE 179
DateIntervalFormat_formatDateRange_DATE_TIME 181
DateIntervalFormat_formatDateRange_TIME 167

ICU4C + JNI
RelativeDateTimeFormatter_getRelativeDateTimeString 151.6
RelativeDateTimeFormatter_getRelativeDateTimeString_ABBREV 169.0
RelativeDateTimeFormatter_getRelativeTimeSpanString  27.8
RelativeDateTimeFormatter_getRelativeTimeSpanString_ABBREV  27.7
ICU4J
RelativeDateTimeFormatter_getRelativeDateTimeString 366.5
RelativeDateTimeFormatter_getRelativeDateTimeString_ABBREV 377.6
RelativeDateTimeFormatter_getRelativeTimeSpanString  23.2
RelativeDateTimeFormatter_getRelativeTimeSpanString_ABBREV  22.9

Bug: 20127691
Change-Id: I1ebc08fd9c974743026ae1e6c848fb4de8aa0e48
7 files changed