fix(VTreeview): correcly handle updating items array of equal size

[nekosaur]

Description

the VTreeview component did not handle updating items prop with an array
of equal size as current array.

Motivation and Context

fixes #6181

How Has This Been Tested?

unit tests and manual playground testing

Markup:

<template>
  <v-app id="inspire">
    <v-treeview
      v-model="tree"
      :open="open"
      :items="items"
      activatable
      item-key="name"
      item-children="children"
      open-on-click
    >
    </v-treeview>
    <v-btn  @click="reload">Test</v-btn>
    <v-btn @click="second">Second</v-btn>
    <v-btn @click="third">Third</v-btn>
  </v-app>
</template>

<script>
export default {
  data: () => ({
    open: ['public'],
    tree: [],
    items: [
      {
        name: 'one'
      },
      {
        name: 'two'
      }
    ]
  }),
  methods: {
    reload () {
      this.items = [
        {
          name: 'one'
        }
      ]
    },
    second () {
      this.items = [
        {
          name: 'one'
        },
        {
          name: 'three'
        }
      ]
    },
    third () {
      this.items = [
        {
          name: 'four'
        },
        {
          name: 'five'
        }
      ]
    }
  }
}
</script>

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Improvement/refactoring (non-breaking change that doesn't add any feature but make things better)

Checklist:

• The PR title is no longer than 64 characters.
• The PR is submitted to the correct branch (master for bug fixes and documentation updates, dev for new features and breaking changes).
• My code follows the code style of this project.
• I've added relevant changes to the documentation (applies to new features and breaking changes in core library)

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[codecov]

Codecov Report

Merging #6202 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #6202      +/-   ##
==========================================
+ Coverage   89.53%   89.54%   +<.01%     
==========================================
  Files         276      276              
  Lines        6318     6323       +5     
  Branches     1594     1594              
==========================================
+ Hits         5657     5662       +5     
  Misses        542      542              
  Partials      119      119

Impacted Files	Coverage Δ
...ages/vuetify/src/components/VTreeview/VTreeview.ts	99.37% <100%> (ø)	⬆️
packages/vuetify/src/util/helpers.ts	91.12% <100%> (+0.37%)	⬆️

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[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs. Please direct any non-bug questions to our Discord