Add a UDF reader and wrapper

[gmipf]

Adds a reader and a wrapper for UDF volumes, so discs without an ISO 9660 file system (dual-layer PC DVDs, BD-Video, HD DVD) can be listed and extracted.

• Volume Recognition Sequence, Anchor Volume Descriptor Pointer (sector 256, then N − 256 and N), Main or Reserve Volume Descriptor Sequence, File Set Descriptor, directory hierarchy
• Type 1 and Metadata Partitions; Virtual and Sparable partitions are not supported
• File Entries and directories are read in ascending sector order with wrap-around, adjacent sectors merged into one request
• FindFileEntry follows one path and reads only the directories on it
• CreateDiscImageWrapper tries UDF after ISO 9660 for a stream at offset 0

Depends on a SabreTools.IO release with SabreTools/SabreTools.IO#3 (0-byte reads at the end of a byte array); with IO 2.3.0 the UDF tests fail.

Measured (the drive runs open /dev/srX as a stream and take its length from sysfs, since FileStream.Length is 0 for a block device):

• 49 Redump PC DVD images without ISO 9660 (38 UDF 1.02, 10 UDF 1.50, 1 UDF 2.01): file count, total size and 7-Zip's SHA256 sum identical for every image
• Street Fighter IV - The Ties That Bind - Bonus Disc (BD-Video, 185 files) and Dragon's Lair HD (HD DVD, 41 files; 7-Zip does not open it), both UDF 2.50 with a Metadata Partition: every file identical to libudfread 1.2.0
• World of WarCraft - Mists of Pandaria - Behind the Scenes (BD, AACS, UDF 2.50 with a Metadata Partition) from a BD drive: all 237 files identical to libudfread reading the same drive
• Hitman: Absolution (Disc 1) (UDF 1.50) from the same drive: all 32 files identical to the Redump image
• Gun (UDF 1.02 with ISO 9660) from a DVD drive, cache dropped before every run: full tree (4573 entries) 37.6 / 37.0 s, kernel udf mount + find 105.3 / 107.0 s, same listing; one file seven directories deep, drive spun down: 4.0 s, kernel mount + read 3.9 s

Tests: reader (on built UDF images), extensions, wrapper.

Prepared with AI assistance (Claude Opus 5.5) and reviewed before submission.