Replace zip crate with rawzip in gix-archive

[Copilot]

Migrates gix-archive from the zip crate to rawzip for ZIP archive creation.

Changes

• Dependencies: Replaced zip = "6.0.0" with rawzip = "0.4.2" and added flate2 to zip feature (required for deflate compression)

• Archive writing (write.rs):

  • Use rawzip::ZipArchiveWriter with explicit flate2::DeflateEncoder for compression
  • Simplify timestamp handling: UtcDateTime::from_unix(seconds) instead of manual date/time component conversion
  • Ensure directory paths end with / (rawzip requirement)

• Tests (archive.rs):

  • Update to rawzip's reading API: ZipArchive::from_slice(), mode().is_symlink(), mode().value(), get_entry().data()
  • Adjust size expectations (rawzip produces ~7% larger archives than zip crate)

API differences

// Old (zip crate)
ar.start_file(path, options)?;
ar.add_directory(path, options)?;

// New (rawzip)
let (mut entry, config) = ar.new_file(path).start()?;
let encoder = flate2::write::DeflateEncoder::new(&mut entry, compression);
let mut writer = config.wrap(encoder);
// ... write data ...

ar.new_dir(&format!("{}/", path)).create()?;  // Must end with '/'

All existing tests pass. The zip crate and its transitive dependencies (arbitrary, derive_arbitrary) are removed from the dependency tree.

Original prompt

Replace the zip crate in gix-archive with https://github.com/nickbabcock/rawzip.

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