[nexus] migrate DNSSD special characters test to Nexus (#12972)

This commit migrates the test for DNSSD names with special characters
from the thread-cert functional tests to the Nexus simulation
framework.

The new Nexus test 'test_dnssd_name_with_special_chars.cpp' replicates
the logic from 'test_dnssd_name_with_special_chars.py' and covers:
- SRP service registration with an instance name containing special
  and Unicode characters ("O\T 网关").
- DNS-SD browse to discover the service instance.
- DNS-SD resolution of the service instance name, including
  verification of case-insensitive resolution.

tests/scripts/thread-cert/test_dnssd_name_with_special_chars.py

@@ -1,117 +0,0 @@
-#!/usr/bin/env python3
-#
-#  Copyright (c) 2021, The OpenThread Authors.
-#  All rights reserved.
-#
-#  Redistribution and use in source and binary forms, with or without
-#  modification, are permitted provided that the following conditions are met:
-#  1. Redistributions of source code must retain the above copyright
-#     notice, this list of conditions and the following disclaimer.
-#  2. Redistributions in binary form must reproduce the above copyright
-#     notice, this list of conditions and the following disclaimer in the
-#     documentation and/or other materials provided with the distribution.
-#  3. Neither the name of the copyright holder nor the
-#     names of its contributors may be used to endorse or promote products
-#     derived from this software without specific prior written permission.
-#
-#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
-#  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
-#  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
-#  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
-#  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
-#  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
-#  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
-#  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
-#  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
-#  POSSIBILITY OF SUCH DAMAGE.
-#
-
-import ipaddress
-import unittest
-import logging
-
-import command
-import config
-import thread_cert
-
-# Test description:
-#   This test verifies SRP/DNS client/server support for Service Instance names with special and unicode characters.
-#
-# Topology:
-#
-#     LEADER (SRP server)
-#       |
-#       |
-#     ROUTER (SRP client)
-#
-
-SERVER = 1
-CLIENT = 2
-
-# TODO: support Instance names with dots (.)
-SPECIAL_INSTANCE_NAME = 'O\\T 网关'
-
-
-class TestDnssdNameWithSpecialChars(thread_cert.TestCase):
-    USE_MESSAGE_FACTORY = False
-    SUPPORT_NCP = False
-
-    TOPOLOGY = {
-        SERVER: {
-            'name': 'SERVER',
-            'mode': 'rdn',
-        },
-        CLIENT: {
-            'name': 'CLIENT',
-            'mode': 'rdn',
-        },
-    }
-
-    def test(self):
-        server = self.nodes[SERVER]
-        client = self.nodes[CLIENT]
-
-        # Start the server & client devices.
-
-        server.start()
-        self.simulator.go(config.LEADER_STARTUP_DELAY)
-        self.assertEqual(server.get_state(), 'leader')
-
-        client.start()
-        self.simulator.go(config.ROUTER_STARTUP_DELAY)
-        self.assertEqual(client.get_state(), 'router')
-
-        server.srp_server_set_enabled(True)
-        client.srp_client_enable_auto_start_mode()
-        self.simulator.go(15)
-
-        # Register a single service with the instance name containing special chars
-        client.srp_client_set_host_name('host1')
-        client.srp_client_set_host_address('2001::1')
-        client.srp_client_add_service(SPECIAL_INSTANCE_NAME, '_srv._udp', 1977)
-        self.simulator.go(5)
-        self.__check_service_discovery(server, client)
-
-    def __check_service_discovery(self, server, client):
-        # Check the service on client
-        client.dns_set_config(server.get_rloc())
-        services = client.dns_browse('_srv._udp.default.service.arpa')
-        self.assertEqual(1, len(services))
-        self.assertIn(SPECIAL_INSTANCE_NAME, services)
-        self.__verify_service(services[SPECIAL_INSTANCE_NAME])
-
-        service = client.dns_resolve_service(SPECIAL_INSTANCE_NAME, '_srv._udp.default.service.arpa')
-        self.__verify_service(service)
-
-        service = client.dns_resolve_service(SPECIAL_INSTANCE_NAME.lower(), '_srv._udp.default.service.arpa')
-        self.__verify_service(service)
-
-    def __verify_service(self, service):
-        logging.info('service discovered: %r', service)
-        self.assertEqual(service['port'], 1977)
-        self.assertEqual(service['host'], 'host1.default.service.arpa.')
-
-
-if __name__ == '__main__':
-    unittest.main()