fix(VDataTable): respect disableSort prop for mobile display mode

[hohanov]

Description

fixes #22998

1. Prevents the VSelect "Sort by" from rendering in the mobile header under either of the following conditions:
   • When the disable-sort prop is active.
   • When all columns have sortable: false configured.
2. Moves the "Select all" VCheckboxBtn into a standalone input component (from VSelect "Sort by" append slot).

inspired by commit c0bdb9c

Markup:

<template>
  <v-app>
    <v-container>
      <v-data-table
        disable-sort
        :headers="headers"
        :items="desserts"
        mobile
        show-select
      ></v-data-table>
    </v-container>
  </v-app>
</template>

<script>
  export default {
    name: 'Playground',
    data() {
      return {
        headers: [
          {
            title: 'Dessert (100g serving)',
            align: 'start',
            key: 'name',
          },
          { title: 'Calories', key: 'calories' },
          { title: 'Fat (g)', key: 'fat' },
          { title: 'Carbs (g)', key: 'carbs' },
          { title: 'Protein (g)', key: 'protein' },
          { title: 'Iron (%)', key: 'iron' },
        ],
        desserts: [
          {
            name: 'Frozen Yogurt',
            calories: 200,
            fat: 6.0,
            carbs: 24,
            protein: 4.0,
            iron: '1%',
          },
          {
            name: 'Ice cream sandwich',
            calories: 200,
            fat: 9.0,
            carbs: 37,
            protein: 4.3,
            iron: '1%',
          },
          {
            name: 'Eclair',
            calories: 300,
            fat: 16.0,
            carbs: 23,
            protein: 6.0,
            iron: '7%',
          },
          {
            name: 'Cupcake',
            calories: 300,
            fat: 3.7,
            carbs: 67,
            protein: 4.3,
            iron: '8%',
          },
          {
            name: 'Gingerbread',
            calories: 400,
            fat: 16.0,
            carbs: 49,
            protein: 3.9,
            iron: '16%',
          },
          {
            name: 'Jelly bean',
            calories: 400,
            fat: 0.0,
            carbs: 94,
            protein: 0.0,
            iron: '0%',
          },
          {
            name: 'Lollipop',
            calories: 400,
            fat: 0.2,
            carbs: 98,
            protein: 0,
            iron: '2%',
          },
          {
            name: 'Honeycomb',
            calories: 400,
            fat: 3.2,
            carbs: 87,
            protein: 6.5,
            iron: '45%',
          },
          {
            name: 'Donut',
            calories: 500,
            fat: 25.0,
            carbs: 51,
            protein: 4.9,
            iron: '22%',
          },
          {
            name: 'KitKat',
            calories: 500,
            fat: 26.0,
            carbs: 65,
            protein: 7,
            iron: '6%',
          },
        ],
      }
    },
  }
</script>