firewall: dnat model "disabled", "ipprotocol" and "protocol" migrations #9859

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For mid-term consideration:

• flip disabled field to enabled
• ipprotocol has "any" and "inet46" options.. removing "inet46" may be beneficial long term as the construct is weird (creating two rules or one without the setting depending on how it is handled underneath)
• protocol is optional and if ipprotocol stays optional remove the XXX from the field definition