[mesh-forwarder] add support for Neighbor Discovery Agent Anycast (#6423)

script/check-scan-build

@@ -68,6 +68,7 @@ do_scan_build()
         "-DOPENTHREAD_CONFIG_MLE_ATTACH_BACKOFF_ENABLE=1"
         "-DOPENTHREAD_CONFIG_MLE_STEERING_DATA_SET_OOB_ENABLE=1"
         "-DOPENTHREAD_CONFIG_MPL_DYNAMIC_INTERVAL_ENABLE"
+        "-DOPENTHREAD_CONFIG_NEIGHBOR_DISCOVERY_AGENT=1"
         "-DOPENTHREAD_CONFIG_PING_SENDER_ENABLE=1"
         "-DOPENTHREAD_CONFIG_PLATFORM_FLASH_API_ENABLE=1"
         "-DOPENTHREAD_CONFIG_PLATFORM_RADIO_COEX_ENABLE=1"

script/cmake-build

@@ -104,6 +104,7 @@ readonly OT_POSIX_SIM_COMMON_OPTIONS=(
     "-DOT_LEGACY=ON"
     "-DOT_MAC_FILTER=ON"
     "-DOT_MTD_NETDIAG=ON"
+    "-DOT_NEIGHBOR_DISCOVERY_AGENT=ON"
     "-DOT_PING_SENDER=ON"
     "-DOT_REFERENCE_DEVICE=ON"
     "-DOT_SERVICE=ON"