test: net:in/out_message tracepoint tests

This adds tests for the net:inbound_message and net:outbound_message
tracepoint interface.

test/functional/test_runner.py

@@ -168,6 +168,7 @@ BASE_SCRIPTS = [
     'wallet_reorgsrestore.py',
     'interface_http.py',
     'interface_rpc.py',
+    'interface_usdt_net.py',
     'rpc_psbt.py --legacy-wallet',
     'rpc_psbt.py --descriptors',
     'rpc_users.py',