Add compression output to repak info command

[Knutschbert]

>repak info MyPak.pak
mount point: ../../../ASD/Content/MyPak/
version: V9
version major: FrozenIndex
encrypted index: false
encryption guid: Some(00000000000000000000000000000000)
compression: Zlib
path hash seed: None
92 file entriess

[trumank]

Perhaps something like this to handle old pak versions that don't have an explicit list of compression methods and also (rare) cases of multiple compression methods? Also would be nice to show an explicit compression: None in the output when no compression is used.

pub fn used_compression(&self) -> Vec<Compression> {
    let mut used_compression = vec![0; self.pak.compression.len()];
    for entry in self.pak.index.entries.values() {
        if let Some(count) = entry
            .compression_slot
            .and_then(|slot| used_compression.get_mut(slot as usize))
        {
            *count += 1;
        }
    }
    used_compression
        .into_iter()
        .zip(self.pak.compression.iter())
        .filter_map(|(count, comp)| comp.filter(|_| count > 0))
        .collect()
}