Add support for packing car files with CIDv0

[0xkarmacoma]

ipfs-car accepts --cidVersion <0|1> flag defaulting to 1, any other value results in an error.

When cidVersion is set to 0, we need to override rawLeaves' value to false, otherwise js-ipfs-unixfs's importer sets the codec to raw instead of dag-pb, which doesn't work with CIDv0