test: fix MIN macro-redefinition

Renames the `MIN` macro to `_TRACEPOINT_TEST_MIN`.

From #31418:

```
stderr:
/virtual/main.c:70:9: warning: 'MIN' macro redefined [-Wmacro-redefined]
   70 | #define MIN(a,b) ({ __typeof__ (a) _a = (a); __typeof__ (b) _b = (b); _a < _b ? _a : _b; })
      |         ^
include/linux/minmax.h:329:9: note: previous definition is here
  329 | #define MIN(a,b) __cmp(min,a,b)
      |         ^
1 warning generated.
```

fixes: bitcoin/bitcoin#31418

test/functional/interface_usdt_net.py

@@ -40,7 +40,8 @@
     MAX_MSG_TYPE_LENGTH,
     MAX_MSG_DATA_LENGTH
 ) + """
-#define MIN(a,b) ({ __typeof__ (a) _a = (a); __typeof__ (b) _b = (b); _a < _b ? _a : _b; })
+// A min() macro. Prefixed with _TRACEPOINT_TEST to avoid collision with other MIN macros.
+#define _TRACEPOINT_TEST_MIN(a,b) ({ __typeof__ (a) _a = (a); __typeof__ (b) _b = (b); _a < _b ? _a : _b; })
 
 struct p2p_message
 {
@@ -60,7 +61,7 @@
     bpf_usdt_readarg_p(3, ctx, &msg.peer_conn_type, MAX_PEER_CONN_TYPE_LENGTH);
     bpf_usdt_readarg_p(4, ctx, &msg.msg_type, MAX_MSG_TYPE_LENGTH);
     bpf_usdt_readarg(5, ctx, &msg.msg_size);
-    bpf_usdt_readarg_p(6, ctx, &msg.msg, MIN(msg.msg_size, MAX_MSG_DATA_LENGTH));
+    bpf_usdt_readarg_p(6, ctx, &msg.msg, _TRACEPOINT_TEST_MIN(msg.msg_size, MAX_MSG_DATA_LENGTH));
     inbound_messages.perf_submit(ctx, &msg, sizeof(msg));
     return 0;
 }
@@ -73,7 +74,7 @@
     bpf_usdt_readarg_p(3, ctx, &msg.peer_conn_type, MAX_PEER_CONN_TYPE_LENGTH);
     bpf_usdt_readarg_p(4, ctx, &msg.msg_type, MAX_MSG_TYPE_LENGTH);
     bpf_usdt_readarg(5, ctx, &msg.msg_size);
-    bpf_usdt_readarg_p(6, ctx, &msg.msg, MIN(msg.msg_size, MAX_MSG_DATA_LENGTH));
+    bpf_usdt_readarg_p(6, ctx, &msg.msg, _TRACEPOINT_TEST_MIN(msg.msg_size, MAX_MSG_DATA_LENGTH));
     outbound_messages.perf_submit(ctx, &msg, sizeof(msg));
     return 0;
 };