Use IDnsResolver instead of INetd for all resolver related commands

1. Make DnsProxyListener get DNS64 prefix internally in libnetd_resolv
2. resolver_test uses IDnsResolver instead of INetd for resolver cmds

Bug: 126141549
Test: built, flashed, booted
       system/netd/tests/runtests.sh pass

Change-Id: Ic904a3efd42ac4011ddd94ff4344449c9e647ceb
13 files changed