Add the remaining FileSystem trait methods to the Windows PassthroughFs: - setxattr, getxattr, listxattr, removexattr: backed by NTFS Alternate Data Streams; override_stat and security.capability streams are protected from direct guest access. - fallocate: extends file length via set_len when offset+length exceeds current size; rejects read-only handles with EBADF. - lseek: handles SEEK_SET/CUR/END/DATA/HOLE arithmetically since all I/O uses explicit offsets. - setupmapping: maps a file region into the guest DAX window via CreateFileMappingW + MapViewOfFileEx with alignment validation. - removemapping: unmaps DAX regions via UnmapViewOfFile. Assisted-by: Cursor:claude-opus-4.6 Signed-off-by: lstocchi <lstocchi@redhat.com>