add nn-cli example (#4373)

an example application with flexible cli options which
aims to allow us to perform any wasi-nn operations.

eg.
```
--load-graph=file=fixture/model.xml,file=fixture/model.bin,id=graph
--init-execution-context=graph-id=graph,id=ctx
--set-input=file=fixture/tensor.bgr,context-id=ctx,dim=1,dim=3,dim=224,dim=224
--compute=context-id=ctx
--get-output=context-id=ctx,file=output.bin
```

wamr-wasi-extensions/samples/nn-cli/map.h

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2025 Midokura Japan KK.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#include <stdint.h>
+
+struct map {
+    struct map_entry {
+        const char *k;
+        uintmax_t v;
+    } * entries;
+    size_t nentries;
+};
+
+void
+map_set(struct map *m, const char *k, uintmax_t v);
+uintmax_t
+map_get(struct map *m, const char *k);