fix(VList): pass return-object to nested VListChildren

[yuwu9145]

Description

v-list prop return-object is not propagating down into the child list items as being set to true.
So what happens is top level items do return a object but a selected child item will return item-value instead of item

Reproduction playground

Markup:

<script setup>
  import { ref } from 'vue';


  const selections = ref([])

  function onOpen() {
    console.log(arguments)
  }

const items = [
  {
   title: 'Option 1',
   subtitle: 'This is option 1',
   value: 1,
  },
  {
    title: 'Option 2',
    subtitle: 'This is option 2',
    value: 2,
    children: [
      {
        title: 'Option 1',
        subtitle: 'This is option 1',
        value: 1,
      },
    ]
  },
]
</script>

<template>
  <v-card class="mx-auto" max-width="400">
    <v-toolbar color="purple">
      <v-btn icon="mdi-menu"></v-btn>

      <v-toolbar-title>Settings</v-toolbar-title>

      <v-spacer></v-spacer>

      <v-btn icon="mdi-magnify"></v-btn>
    </v-toolbar>

    <v-divider></v-divider>

    <v-list
      selectable
      v-model:selected="selections"
      @click:open="onOpen"
      :items="items"
      lines="three"
      select-strategy="classic"
      return-object
    />

    <pre>{{ selections }}</pre>
  </v-card>
</template>