Remove the KVDB-to-SQL migration from the dev SQL migration set now
that this migration is now part of the production migration set.
As the migrations_dev folder no longer contains any migrations, we also
update the db logic and the gen_sqlc_docker.sh script to not error when
the folder(s) are empty.
Move the programmatic KVDB-to-SQL migration out of the dev-only
migration stream and into the production SQL migration set.
This also requires that we add a new migration file for the prod
migration, which will trigger the kvdb to sql programmatic migration to
run in production.
With the latest version of the `sqldb/v2` & `migrate` packages, Post
Migration Callbacks were renamed to Programmatic Migrations.
Our previous codebase still had some mentions of Post Migration
Callbacks, and therefore we rename those to use the word Programmatic
Migrations instead.
