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/CMakeLists.txt

@@ -0,0 +1,12 @@
+# Copyright (C) 2025 Midokura Japan KK.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+cmake_minimum_required(VERSION 3.14)
+
+set(CMAKE_C_STANDARD 99)
+set(CMAKE_C_STANDARD_REQUIRED YES)
+
+project(nn-cli LANGUAGES C)
+add_executable(nn-cli main.c fileio.c map.c)
+find_package(wamr-wasi-nn REQUIRED)
+target_link_libraries(nn-cli wamr-wasi-nn)