fix(VDateInput): apply readonly

[SonTT19]

Description

fixes #20147

Markup:

<template>
  <v-app>
    <v-container>
      <v-date-input v-model="date" readonly></v-date-input>
    </v-container>
  </v-app>
</template>

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

  const date = ref(new Date())
</script>

[MatthewAry]

I believe the guard would be better placed in this function:

https://github.com/vuetifyjs/vuetify/blob/f0fa4e6e705508699cb2013d322d8ce9b204a8d5/packages/vuetify/src/labs/VDateInput/VDateInput.tsx#L88C14-L93

[johnleider]

I made some adjustments to handle keyboard interaction and also disabled state.