Based on test_pkt_normalizer_etcp.c but uses high-level API:
- etcp_send() for sending packets via ETCP normalizer
- etcp_bind() for registering receive callbacks
- etcp_api_init()/etcp_api_deinit() for API lifecycle
NOTE: Test has current limitation - pkt_normalizer packer aggregates
packets into ~1536 byte chunks, exceeding ETCP max payload of 1480 bytes.
This causes encrypt_send to fail. The test demonstrates correct API usage
pattern but requires packer fix for full functionality.