[RFCLAT#4] Move clat ipv6 address setup from clatd to netd

This is a preparation for reducing the clatd required capability.

Function change:
- configure_clat_ipv6_address(), configure_interface(),
  configure_packet_socket() are moved to netd/ClatdController
- move the follows to main() because previous functions are removed.
  setup Global_Clatd_Config.native_ipv6_interface
  setup Global_Clatd_Config.plat_subnet
  setup Global_Clatd_Config.ipv6_local_subnet

Bug: 212345928
Test: manual test
1. Connect to ipv6-only wifi.
2. Try IPv4 traffic.
   $ ping 8.8.8.8

Change-Id: I8457b7752a799756549a72296aae572ad73ff653
3 files changed