Update Gitlab.com deployments to use the "database.primary" config to run migrations in gstg and gprd

Context

Following from Add a new registry config for specifying the pr... (#1142 - closed) we need to now set the appropriate values for

 database:
    primary: my.primary.postgres.server

in Gitlab.com gstg and gprd k8s deployment in order for schema migrations (including post deploy migrations) to be able to targer the primary postgres server.

Note: for Gitlab.com (both gstg and gprd environments) the fqdn of the primary server should be master.patroni-registry.service.consul

Tasks

• Set the registry's database.primary value in gstg to master.patroni-registry.service.consul
• Deploy and monitor the outcome in gstg
• If the last step was successful repeat the first two steps for gprd
• If any steps were unsuccessful, rollback changes and work with infra team to figure out why