fix(VWindow): fix wrong reverse animation logic for only 2 items

[yuwu9145]

fixes #12672

Description

Issue #12672 is caused by a recent change from PR 12357. Its change results in wrong animation reverse logic when items length is less than 3.

This pull request is making it fully support all items length in terms of animation reverse logic on top of the code from PR 12357.

@nekosaur please help to check it out to see this change would raise any concerns from you and please also feel free to leave any feedback :).

Motivation and Context

closes #12672

How Has This Been Tested?

visually

Markup:

<template>
  <v-container>
    <v-card>
      <v-toolbar flat>
        <template v-slot:extension>
          <v-tabs
            v-model="tabs"
            fixed-tabs
          >
            <v-tabs-slider></v-tabs-slider>
            <v-tab
              href="#mobile-tabs-5-1"
              class="primary--text"
            >
              <v-icon>mdi-phone</v-icon>
            </v-tab>

            <v-tab
              href="#mobile-tabs-5-2"
              class="primary--text"
            >
              <v-icon>mdi-heart</v-icon>
            </v-tab>
          </v-tabs>
        </template>
      </v-toolbar>

      <v-tabs-items v-model="tabs">
        <v-tab-item
          v-for="i in 2"
          :key="i"
          :value="'mobile-tabs-5-' + i"
        >
          <v-card flat>
            <v-card-text v-text="text"></v-card-text>
          </v-card>
        </v-tab-item>
      </v-tabs-items>
    </v-card>
  </v-container>
</template>

<script>
  export default {
    data () {
      return {
        tabs: null,
        text: 'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.',
      }
    },
    methods: {
    }
  }
</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 features but makes 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 backwards compatible changes and next for non-backwards compatible 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)

[yuwu9145]

@nekosaur , please help to check if this change is compatible with fixing issue #11280 from this PR.

Thank you in advance :)

[yuwu9145]

@MajesticPotatoe @nekosaur , I checked out myself, this PR respects the fix for this issue from PR 12357

[MajesticPotatoe]

👍
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