Rename the session_id to group_id in kvstores table in the SQL store, to
better represent how the field is actually used.
Note that this is a breaking change, and would normally require a new
migration. But as the SQL store is not used in production, and only
enabled under the dev build flag, we can rename it without a new
migration, as there's no users of the SQL store in production.
During the upcoming upcoming migration of the firewall database to SQL,
we need to be able to check all kvstores records in the SQL database,
to validate that the migration is successful in tests.
This commits adds a query to list all kvstores records, which enables
that functionality.
