CVE-2025-13462 tarfile: Skip DIRTYPE normalization during GNU LONGNAME/LONGLINK handling

The "tarfile" module would still apply normalization of AREGTYPE \x00 blocks to DIRTYPE, even while processing a multi-block member such as GNUTYPELONGNAME or GNUTYPELONGLINK. This could result in a crafted tar archive being misinterpreted by the tarfile module compared to other implementations...