`NATReconciler` should only modify the `NATTable` of `NetworkInterfaces` belonging to the NATs `networkRef`

[afritzler]

Describe the bug
It seems like the NATReconciler is applying the NATs public IP to all NICs in the namespace of a given NATGateway. That leads to a problem if you have multiple Networks but only one is using a NAT. In the current NATTable logic the we are doing a client.List on all in-namespace NICs which leads to a situation where all NICs regardless of their Network having a NAT or not will get a public IP.

/cc @hardikdr