fix(runtime-core): make cache indexes marker non-enumerable in initSlots

Author: edison1105

packages/runtime-core/src/componentSlots.ts

@@ -193,6 +193,10 @@ export const initSlots = (
 ): void => {
   const slots = (instance.slots = createInternalObject())
   if (instance.vnode.shapeFlag & ShapeFlags.SLOTS_CHILDREN) {
+    const cacheIndexes = (children as RawSlots).__
+    // make cache indexes marker non-enumerable
+    if (cacheIndexes) def(slots, '__', cacheIndexes, true)
+
     const type = (children as RawSlots)._
     if (type) {
       assignSlots(slots, children as Slots, optimized)