Merge libnetddns into libnetd_resolv

libnetddns is the library for DNS-over-TLS and is statically
linked to netd. Deprecate it and move them to libnetd_resolv
as a more general DNS library for netd.

This change comprises:

[1] Clean up netd/server/dns/*. Move all DnsTls* files to
    netd/resolv/ to parts of libnetd_resolv library.

[2] Export DnsTls* classes being visible for netd. It will only
    be temporary for a while.

[3] Remove the libssl dependency in netd. The relevant stuff is
    moved to libnetd_resolv.

Note that DnsTls* classes are still required for DnsProxyListener
and ResolverController to manipulate private DNS servers even after
this change.

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

Change-Id: Ieac5889b4ebe737f876b3dcbe1a8da2b2b1b629d
diff --git a/resolv/include/netd_resolv/params.h b/resolv/include/netd_resolv/params.h
index 60b9b54..c3f3363 100644
--- a/resolv/include/netd_resolv/params.h
+++ b/resolv/include/netd_resolv/params.h
@@ -46,4 +46,7 @@
 
 #define LIBNETD_RESOLV_PUBLIC extern "C" [[gnu::visibility("default")]]
 
+// TODO: Remove it after we move PrivateDnsConfiguration and qhook() into libnetd_resolv.
+#define LIBNETD_RESOLV_TLS_EXPORT [[gnu::visibility("default")]]
+
 #endif  // NETD_RESOLV_PARAMS_H