Refactor interface IP code into InterfaceController

Test: as follows
    - built
    - flashed
    - booted
    - runtest frameworks-net passes
      (except for UidRange and APF tests that are missing libvndk)
    - regular WiFi STA mode attach works for IPv4-only, dualstack,
      and IPv6-only networks
    - tethering works with dualstack upstream and downstream
Bug: 62476366

Change-Id: Id807b3091b0b2935b01aeb3644245034312b4183