[combiner] Move all INFO fields to entries (#5678)
[combiner] Move all INFO fields to entries (#5678)

* [combiner] update in response to feedback

Store all info fields from initial gvcfs in entries. Add function to
compute the info fields that do not require densification.

* Add ceiling to VarDP on import.

For some reason, some variants have a VarDP of 2^31-1, previously we
were wrapping them with hl.sum over an array during combining. With the
switch to moving everything to entries and using aggregations, this was
now summing as type int64, which would get out of range, causing
export_vcf to fail. After discussing with @ldgauthier, exclude anything
above some threshold, by default 100,000, setting it to DP instead.

* Update gvcf_combiner schema reference

danking/hail,cseed/hail,hail-is/hail,danking/hail,hail-is/hail,danking/hail,hail-is/hail,danking/hail,danking/hail,hail-is/hail,hail-is/hail,cseed/hail,danking/hail,cseed/hail,hail-is/hail,danking/hail,danking/hail,cseed/hail,cseed/hail,cseed/hail,cseed/hail,hail-is/hail,cseed/hail,hail-is/hail