sevenz-rust2: unchecked 7z entry paths permit traversal and absolute-path file overwrites

sevenz-rust2 is a Rust-native 7z compressor and decompressor. Prior to 0.21.1, extracting an attacker-supplied 7z archive can write or overwrite files outside the destination directory. In src/util/decompress.rs, decompress_impl computes each destination with dest.join(entry.name()) without normalizing the archive's UTF-16 entry name or verifying containment, and default_entry_extract_fn writes to it with File::create. Parent-directory components escape the extraction root, and an absolute entry path makes the join discard the destination entirely. The convenience entry points decompress, decompress_file, decompress_with_password, and decompress_file_with_password all use this default path. Overwriting writable configuration, startup, cron, or build files can lead to code execution or persistence. The archive bytes are the attacker-controlled trust boundary, including for applications that automatically unpack uploaded or otherwise untrusted archives. This issue is fixed in version 0.21.1.