fs/ntfs3: implement llseek SEEK_DATA/SEEK_HOLE by scanning data runs

fs/ntfs3: implement llseek SEEK_DATA/SEEK_HOLE by scanning data runs

The generic llseek implementation does not understand ntfs data runs,
sparse regions, or compression semantics, and therefore cannot correctly
locate data or holes in files.

Add a filesystem-specific llseek handler that scans attribute data runs
to find the next data or hole starting at the given offset. Handle
resident attributes, sparse runs, compressed holes, and the implicit hole
at end-of-file.

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>