xfs_scrub: make name_entry a first class structure

xfs_scrub: make name_entry a first class structure

Instead of open-coding the construction and hashtable insertion of name
entries, make name_entry a first class object.  This means that we now
have name_entry_ prefix functions that take care of computing Unicode
normalized names as part of name_entry construction, and we pass around
the name_entries when we're looking for suspicious characters and
identically rendering names.

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>