feat: add new input prop **clear-value**

[johnleider]

allows setting a custom value to use on clear

resolves #4144

Description

Markup:

<template>
  <v-container class="pa-md-12">
    <v-select v-model="select1" :items="['Foo', 'Bar']" clearable /> {{ select1 }}
    <v-select v-model="select2" :items="['Foo', 'Bar']" clearable multiple /> {{ select2 }}
    <v-autocomplete v-model="auto1" :items="['Foo', 'Bar']" clearable /> {{ auto1 }}
    <v-autocomplete v-model="auto2" :items="['Foo', 'Bar']" clearable multiple /> {{ auto2 }}

    <!-- <v-text-field v-model="text" :clear-value="''" clearable="" />
    <v-textarea model-value="foobar" clearable />
    <v-autocomplete v-model="auto" :clear-value="onClear" :items="['Foo', 'Bar']" clearable />
    <v-combobox v-model="combo" :clear-value="onClear" :items="['Foo', 'Bar']" clearable />
    <v-file-input v-model="files" clearable multiple />
    <v-date-input v-model="dates" clearable multiple /> -->
  </v-container>
</template>

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

  const dates = ref([])
  const files = ref([])
  const select1 = ref('Foo')
  const select2 = ref(['Foo'])
  const text = ref('Fas')
  const auto1 = ref('Foo')
  const auto2 = ref(['Foo'])
  const combo = ref('Foo')

  function onClear () {
    return ''
  }
</script>