Make wasi-nn backends as separated shared libraries (#3509)

- All files under *core/iwasm/libraries/wasi-nn* are compiled as shared libraries
- *wasi-nn.c* is shared between backends
- Every backend has a separated shared library
- If wasi-nn feature is enabled, iwasm will depend on shared library libiwasm.so
  instead of linking static library libvmlib.a

core/iwasm/interpreter/wasm_runtime.c

@@ -3181,9 +3181,6 @@ wasm_deinstantiate(WASMModuleInstance *module_inst, bool is_sub_inst)
         wasm_runtime_free(module_inst->c_api_func_imports);
 
     if (!is_sub_inst) {
-#if WASM_ENABLE_WASI_NN != 0
-        wasi_nn_destroy((WASMModuleInstanceCommon *)module_inst);
-#endif
         wasm_native_call_context_dtors((WASMModuleInstanceCommon *)module_inst);
     }