[mac] add enhanced frame pending (#4334)

This commit adds enhanced frame pending feature of Thread 1.2. This
requires the platform radio driver to correctly set frame pending bit
for Data frames and MAC Data Request frames.

tests/scripts/thread-cert/ipv6.py

@@ -34,6 +34,8 @@ import struct
 from binascii import hexlify
 from ipaddress import ip_address
 
+import common
+
 try:
     from itertools import izip_longest as zip_longest
 except ImportError:
@@ -1079,7 +1081,10 @@ class UdpBasedOnSrcDstPortsPayloadFactory:
         if message_info.src_port in self._factories:
             factory = self._factories[message_info.src_port]
 
-        if factory is None:
+        if message_info.dst_port == common.UDP_TEST_PORT:
+            # Ignore traffic targeted to test port
+            return None
+        elif factory is None:
             raise RuntimeError("Could not find factory to build UDP payload.")
 
         return factory.parse(data, message_info)