Issue #421: Update opensearch gnomad mappings to match updates hg19 a…

…nd hg38 data (#431)

* Updates hg38.mapping.yamland hg19.mapping.yaml to support new our new
hg19 and hg38 databases
* Updates hg38.clean.yml and hg19.clean.yml to match the bystro
annotator definitions of our new databases

hg38.mapping.yml is now a separate definition, rather than a symlink to
hg19.mapping.yml. It is identical to hg19.mapping.yml besides the gnomad
sections, which have to be different since gnomad v4 was used in the
hg38 database.