[tests] add tests for Border Routing Counters (#8341)

This commit adds tests for verifying the functionality of the D-BUS
API `GetBorderRoutingCounters`.

tests/scripts/thread-cert/call_dbus_method.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+#
+#  Copyright (c) 2022, 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 dbus
+import json
+import sys
+
+
+def main():
+    args = sys.argv[1:]
+    bus = dbus.SystemBus()
+    interface, method_name, arguments = args[0], args[1], args[2:]
+    obj = bus.get_object('io.openthread.BorderRouter.wpan0', '/io/openthread/BorderRouter/wpan0')
+    iface = dbus.Interface(obj, interface)
+    method = getattr(iface, method_name)
+    res = method(*arguments)
+    print(json.dumps(res))
+
+
+if __name__ == '__main__':
+    main()