Implement bind-to-network functionality of android.net.Network.

This is implemented by calling through to netd_client.
Included are functions to bind-to-network-for-process strictly for DNS to
facilitate startUsingNetworkFeature() reimplementation.

bug: 13885501

Change-Id: Ib22c7d02ea81d251bdfeeb0f64a47ce32eefcb1b
(cherry picked from commit dbf76f898f1f57eb74722358087c926d2f529bda)