[nexus] migrate CoAP block transfer test to Nexus (#13003)

This commit migrates the functionality covered by test_coap_block.py
to the Nexus test framework.

- Enabled OPENTHREAD_CONFIG_COAP_BLOCKWISE_TRANSFER_ENABLE in Nexus
  config.
- Created test_coap_block.cpp to test CoAP GET and PUT block
  transfers in a simulated network.
- Removed the old Python test test_coap_block.py.

tests/scripts/thread-cert/test_coap_block.py

@@ -1,108 +0,0 @@
-#!/usr/bin/env python3
-#
-#  Copyright (c) 2020, 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 unittest
-
-import pexpect
-import config
-import thread_cert
-
-LEADER = 1
-ROUTER = 2
-
-
-class TestCoapBlockTransfer(thread_cert.TestCase):
-    """
-    Test suite for CoAP Block-Wise Transfers (RFC7959).
-    """
-
-    SUPPORT_NCP = False
-
-    TOPOLOGY = {
-        LEADER: {
-            'mode': 'rdn',
-            'whitelist': [ROUTER]
-        },
-        ROUTER: {
-            'mode': 'rdn',
-            'whitelist': [LEADER]
-        },
-    }
-
-    def test(self):
-        leader = self.nodes[LEADER]
-        router = self.nodes[ROUTER]
-
-        leader.start()
-        self.simulator.go(config.LEADER_STARTUP_DELAY)
-        self.assertEqual(leader.get_state(), 'leader')
-
-        router.start()
-        self.simulator.go(config.ROUTER_STARTUP_DELAY)
-        self.assertEqual(router.get_state(), 'router')
-
-        leader_mleid = leader.get_ip6_address(config.ADDRESS_TYPE.ML_EID)
-        router_mleid = router.get_ip6_address(config.ADDRESS_TYPE.ML_EID)
-
-        leader.coap_set_resource_path_block('test', 3)
-
-        leader.coap_start()
-        router.coap_start()
-
-        for method in ['GET', 'PUT', 'POST']:
-            if method == 'GET':
-                response = router.coap_get_block(leader_mleid, 'test', size=32)
-            elif method == 'PUT':
-                response = router.coap_put_block(leader_mleid, 'test', size=256, count=2)
-            elif method == 'POST':
-                response = router.coap_post_block(leader_mleid, 'test', size=1024, count=2)
-            else:
-                raise ValueError(method)
-
-            self.assertEqual(response['source'], leader_mleid)
-
-            request = leader.coap_wait_request()
-            self.assertEqual(request['method'], method)
-            self.assertEqual(request['source'], router_mleid)
-
-            if method == 'GET':
-                self.assertIsNotNone(response['payload'])
-                self.assertIsNone(request['payload'])
-            else:
-                self.assertIsNone(response['payload'])
-                self.assertIsNotNone(request['payload'])
-
-            self.simulator.go(10)
-
-        router.coap_stop()
-        leader.coap_stop()
-
-
-if __name__ == '__main__':
-    unittest.main()