Cherry-pick: ICU-21455 Add new API ubrk_clone() and deprecate ubrk_safeClone() am: 16f37a65cd

Original change: https://android-review.googlesource.com/c/platform/external/icu/+/1581884

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I3ced8d9b5378b4d4072aa6f438dca850fbbf46cd