Add two Netd binder calls to set/get resolver config.

setResolverConfiguration() sets the name servers, search domains,
and resolver parameters.
getResolverInfo() returns the configured information and also the
statistics for each server.
Also includes tests for the new functionality.

BUG: 25731675

Change-Id: Idde486f36bb731f9edd240d62dc1795f8e621fe6