assert_vcfs_close doesn't handle missingness subtlety #14
Description
As predicted @tomwhite we've hit sgkit-dev/vcf-zarr-spec#11 pretty quickly when adding tests on real VCF files. I added a quick cludge to workaround the first case I hit, but it would be good to handle this more systematically. Unfortunately, I think it will just need a some ugly code like we have in the validation code in vcf2zarr here