Add outbound_addr to allow for SNAT instead of MASQ

[lto-dev]

Added outbound_addr to the bridge driver.

I created a bridge-snat plugin to use this feature and do SNAT instead of MASQUERADE on certain networks since i have multiple public ip's on same machine and i needed the traffic to go out on them and not on the gateway.
I can share the plugin as well if anyone wants it.

[openshift-ci]

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[Luap99]

please add proper integration test in test/ for both iptables and nftables

I have not yet looked into the rules that are added and if they are correct

Also I think this would need to be added to the firewalld code as well cc @mheon

[lto-dev]

let me know if the modifications are ok

[Luap99]

Note I do not have time to properly review the rules right now. However please make sure your commits make sense as individual unit. Currently they are pretty meaningless so I suggest you squash everything into one