Merge changes from topic \'icu_cp_catchup\' am: f6aabd95

am: 2b44297f

* commit '2b44297f':
  Track external/icu API changes for factory registration
  ICU4J: Hide constants that can change between releases
  Remove RawCollationKey/ByteArrayWrapper from the public API

Change-Id: I485a59fa5a565d6916c9eed1e03dce3d01145a4e