Support for NSEC3 in dnssec-policy

Implement support for NSEC3 in dnssec-policy.  Store the configuration
in kasp objects. When configuring a zone, call 'dns_zone_setnsec3param'
to queue an nsec3param event. This will ensure that any previous
chains will be removed and a chain according to the dnssec-policy is
created.

Add tests for dnssec-policy zones that uses the new 'nsec3param'
option, as well as changing to new values, changing to NSEC, and
changing from NSEC.

bin/tests/system/nsec3/setup.sh

@@ -0,0 +1,24 @@
+#!/bin/sh -e
+#
+# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, you can obtain one at https://mozilla.org/MPL/2.0/.
+#
+# See the COPYRIGHT file distributed with this work for additional
+# information regarding copyright ownership.
+
+# shellcheck source=conf.sh
+. ../conf.sh
+
+set -e
+
+$SHELL clean.sh
+
+copy_setports ns3/named.conf.in ns3/named.conf
+
+(
+	cd ns3
+	$SHELL setup.sh
+)