fix(prerender): flatten hAsync children to resolve promises

src/hydrate/platform/h-async.ts

@@ -1,15 +1,16 @@
-import * as d from '../../declarations';
+import type * as d from '../../declarations';
+import { consoleDevError } from '@platform';
 import { h } from '@runtime';
 import { isPromise } from '@utils';
-import { consoleDevError } from '@platform';
 
 export const hAsync = (nodeName: any, vnodeData: any, ...children: d.ChildType[]) => {
   if (Array.isArray(children) && children.length > 0) {
     // only return a promise if we have to
-    if (children.some(isPromise)) {
+    const flatChildren = children.flat(Infinity);
+    if (flatChildren.some(isPromise)) {
       // has children and at least one of them is async
       // wait on all of them to be resolved
-      return Promise.all(children)
+      return Promise.all(flatChildren)
         .then(resolvedChildren => {
           return h(nodeName, vnodeData, ...resolvedChildren);
         })