Merge PrivateDnsConfiguration and qhook into libnetd_resolv
PrivateDnsConfiguration handles the operations which adds, validates,
and removes private DNS servers. It will be hidden inside the library
after this change.
PrivateDnsConfiguration and DnsTlsDispatcher will be constructed along
with netd starts. Their instances are now moved to the library. Netd
can use public functions to update private DNS servers. In addition,
qhook() is no longer needed for TLS query.
This change comprises:
 Provide APIs for netd to add and delete private DNS servers as
well as get status.
 Provide a way for netd to register callback which will be invoked
whenever private DNS servers validation finishes. This is used for
 Remove qhook in android_net_context, since DnsTls* have been moved
to libnetd_resolv library. Also, qhook and rhook are removed in the
 The visibility of DnsTls* symbols are hidden, while they have been
visible for a while.
Test: as follows
- built, flashed, booted
- DNS-over-TLS in live network passed
17 files changed