Add haproxy_action to the schema
We add a new action to the schema to allow the user to configure actions that will be evaluated by haproxy.
We decided not to support rate limiting in haproxy because using stick tables can be problematic for performance without tight control. On the other hand, we support both denying a request properly and silent-dropping it. In addition, bandwidth limiting is also supported.
The ancillary object to store the dsl output is also added.
Bug: T369606