Refactor WASI-NN to simplify the support for multiple frameworks (#1834)

- Reorganize the library structure
- Use the latest version of `wasi-nn` wit (Oct 25, 2022):
    0f77c48ec1/wasi-nn.wit.md
- Split logic that converts WASM structs to native structs in a separate file
- Simplify addition of new frameworks

core/iwasm/interpreter/wasm_runtime.c

@@ -1803,6 +1803,16 @@ wasm_instantiate(WASMModule *module, bool is_sub_inst, uint32 stack_size,
     }
 #endif
 
+#if WASM_ENABLE_WASI_NN != 0
+    if (!is_sub_inst) {
+        if (!(module_inst->e->wasi_nn_ctx = wasi_nn_initialize())) {
+            set_error_buf(error_buf, error_buf_size,
+                          "wasi nn initialization failed");
+            goto fail;
+        }
+    }
+#endif
+
 #if WASM_ENABLE_DEBUG_INTERP != 0                         \
     || (WASM_ENABLE_FAST_JIT != 0 && WASM_ENABLE_JIT != 0 \
         && WASM_ENABLE_LAZY_JIT != 0)
@@ -1984,6 +1994,14 @@ wasm_deinstantiate(WASMModuleInstance *module_inst, bool is_sub_inst)
     if (module_inst->e->c_api_func_imports)
         wasm_runtime_free(module_inst->e->c_api_func_imports);
 
+#if WASM_ENABLE_WASI_NN != 0
+    if (!is_sub_inst) {
+        WASINNContext *wasi_nn_ctx = module_inst->e->wasi_nn_ctx;
+        if (wasi_nn_ctx)
+            wasi_nn_destroy(wasi_nn_ctx);
+    }
+#endif
+
     wasm_runtime_free(module_inst);
 }