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:

[1] Provide APIs for netd to add and delete private DNS servers as
    well as get status.

[2] Provide a way for netd to register callback which will be invoked
    whenever private DNS servers validation finishes. This is used for
    onPrivateDnsValidationEvent().

[3] Remove qhook in android_net_context, since DnsTls* have been moved
    to libnetd_resolv library. Also, qhook and rhook are removed in the
    library.

[4] The visibility of DnsTls* symbols are hidden, while they have been
    visible for a while.

Bug: 113628807
Test: as follows
    - built, flashed, booted
    - system/netd/tests/runtests.sh
    - DNS-over-TLS in live network passed

Change-Id: I235004e4019d88d0d162d7ebd452148cd14cfd39
17 files changed