Move icu related hidden API flag file contents from frameworks/base

Added OWNERS files and PREUPLOAD.cfg entry to maintain the files.

Bug: 179354495
Test: verified that the monolithic hidden api files in out/soong/hiddenapi/... are unchanged
      by this change
      also verified that changes to these files do affect the monolithic files.
Change-Id: I7c2a57b3ad3deb901d3e062eda0181ed4928f75a
4 files changed
tree: 1941f4ffba19be72bc3c5e0de128e8609430c597
  1. apex/
  2. PREUPLOAD.cfg