fix(warning): stringify args in warn handler (#10414)

close #10409

packages/runtime-core/src/warning.ts

@@ -45,7 +45,7 @@ export function warn(msg: string, ...args: any[]) {
       instance,
       ErrorCodes.APP_WARN_HANDLER,
       [
-        msg + args.join(''),
+        msg + args.map(a => a.toString?.() ?? JSON.stringify(a)).join(''),
         instance && instance.proxy,
         trace
           .map(