[nexus] add test 9.2.13 Energy Scan Requests (#12551)

This commit adds Nexus test case 9.2.13 which verifies that the Thread
device properly accepts and processes Energy Scan Requests and sends
the corresponding Energy Scan Reports.

Implementation details:
- tests/nexus/test_9_2_13.cpp: C++ test execution logic. Implements
  the 9.2.13 spec using direct core calls. Manages two separate
  networks (Network 1 on channel 11 and Network 2 on channel 12).
  Configures a topology with Leader, Commissioner, Router, and FED
  nodes in Network 1, and Leader and SED nodes in Network 2.
- tests/nexus/verify_9_2_13.py: PCAP verification script. Verifies
  unicast and multicast MGMT_ED_SCAN.qry messages and the resulting
  MGMT_ED_REPORT.ans responses. Uses strict CoAP URI path and ICMPv6
  type filtering.
- tests/nexus/platform/nexus_core.hpp/cpp: Added an optional leader
  node parameter to SaveTestInfo() to allow specifying which network
  partition information (like Network Key and Mesh-Local Prefix)
  should be exported to the JSON file for verification. This ensures
  correct packet dissection in multi-partition test scenarios.
- tests/nexus/run_nexus_tests.sh: Added 9_2_13 to default test list.
- tests/nexus/CMakeLists.txt: Added nexus_9_2_13 target.

tests/scripts/thread-cert/pktverify/consts.py

@@ -213,6 +213,8 @@ NM_JOINER_ROUTER_KEK_TLV = 21
 NM_PENDING_TIMESTAMP_TLV = 51
 NM_DELAY_TIMER_TLV = 52
 NM_CHANNEL_MASK_TLV = 53
+NM_COUNT_TLV = 54
+NM_PERIOD_TLV = 55
 NM_SCAN_DURATION = 56
 NM_ENERGY_LIST_TLV = 57
 NM_DISCOVERY_REQUEST_TLV = 128