xfs_scrub: transition from libunistring to libicu for Unicode processing

xfs_scrub: transition from libunistring to libicu for Unicode processing

Move off of libunistring and onto libicu for Unicode name scanning.
This will make it easy to warn about unicode code points that do not
belong in identifiers (directional overrides, zero width elements) and
warn about names that could render similarly enough to cause confusion.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Acked-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>