feat(VVirtualScroll): port to v3

[nekosaur]

Description

BREAKING CHANGES

• bench prop removed

Motivation and Context

How Has This Been Tested?

Markup:

<template>
  <v-app>
    <div class="pa-4 h-100">
      <v-virtual-scroll :items="items" height="800" item-height="48" dynamic-item-height>
        <template #default="{ item, index }">
          <div
            :class="[
              index % 2 === 0 ? 'pa-2' : index % 5 == 0 ? 'pa-8' : 'pa-4',
              index % 2 === 0 ? 'bg-primary' : 'bg-secondary'
            ]"
          >
            I'm item item {{ item }} (index {{ index }})
          </div>
        </template>
      </v-virtual-scroll>

      <v-select :items="items" label="Foo"></v-select>
    </div>
  </v-app>
</template>

<script>
  export default {
    data: () => ({
      drawer: false,
      count: 10000,
    }),

    computed: {
      items () {
        return Array.from({ length: this.count }, (k, v) => v + 1)
      },
    },
  }
</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)