fix(nested): prevent parent node activate firing for singleLeaf

[yuwu9145]

Description

fixes #20946

Markup:

<template>
  <v-treeview
    @update:activated="args => console.log('activated', args)"
    :items="items"
    :opened="initiallyOpen"
    item-value="title"
    activatable
    active-strategy="single-leaf"
    open-all
  >
    <template v-slot:prepend="{ item, isOpen }">
      <v-icon v-if="!item.file">
        {{ isOpen ? 'mdi-folder-open' : 'mdi-folder' }}
      </v-icon>
      <v-icon v-else> {{ files[item.file] }} </v-icon>
    </template>
  </v-treeview>
</template>

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

  const initiallyOpen = ref(['public'])
  const files = ref({
    html: 'mdi-language-html5',
    js: 'mdi-nodejs',
    json: 'mdi-code-json',
    md: 'mdi-language-markdown',
    pdf: 'mdi-file-pdf-box',
    png: 'mdi-file-image',
    txt: 'mdi-file-document-outline',
    xls: 'mdi-file-excel',
  })
  const items = ref([
    {
      title: '.git',
    },
    {
      title: 'node_modules',
    },
    {
      title: 'public',
      children: [
        {
          title: 'static',
          children: [
            {
              title: 'logo.png',
              file: 'png',
            },
          ],
        },
        {
          title: 'favicon.ico',
          file: 'png',
        },
        {
          title: 'index.html',
          file: 'html',
        },
      ],
    },
    {
      title: '.gitignore',
      file: 'txt',
    },
    {
      title: 'babel.config.js',
      file: 'js',
    },
    {
      title: 'package.json',
      file: 'json',
    },
    {
      title: 'README.md',
      file: 'md',
    },
    {
      title: 'vue.config.js',
      file: 'js',
    },
    {
      title: 'yarn.lock',
      file: 'txt',
    },
  ])
</script>

[yuwu9145]

@KaelWD What do you think of this change?

[KaelWD]

If they're already sets .has should be faster than .includes

[yuwu9145]

Refactored to use symmetricDifference instead

[KaelWD]

We can't use these yet unfortunately: https://caniuse.com/mdn-javascript_builtins_set_symmetricdifference