Add the planned set of new I18N public APIs for
Android N.
This APIs consists of a whitelisted subset of ICU4J APIs
repackaged under android.icu (not com.ibm.icu).
It includes no deprecated, provisional, internal methods from
ICU 56.
There may be future work to improve the ICU4J JavaDoc text
for Android, but the API surface area should be mostly
stable at this point.
Bug: 22023363
(cherry-picked from commit d7fa3e79f071696bd62182c01b62fe0ea1cc9587)
Change-Id: I6667acbbf7c5501e12ecfbdd560ea80283c0c831
ebd7735baa