fix(validation): a disabled field should always be valid

[johnleider]

Motivation and Context

Skip validation if disabled.

TODO: Should this occur on readonly as well? Yes

Markup:

<template>
  <v-container class="pa-md-12">
    <v-form v-model="valid">
      <v-text-field :rules="[val => !!val || 'Required']" label="Regular" />
      <v-text-field :rules="[val => !!val || 'Required']" label="Disabled" disabled />
    </v-form>

    <pre>{{ JSON.stringify(valid, null, 2) }}</pre>
  </v-container>
</template>

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

  const valid = ref(false)
</script>