feat(VRow): add responsive gap props

[J-Sek]

Adds gap-{sm/md/lg/xl/xxl} props to VRow

resolves #23232

<template>
  <v-app theme="dark">
    <v-container>
      <h3 class="mb-2">VRow responsive gap ({{ $vuetify.display.name }})</h3>
      <v-row :gap="[4, 4]" :gap-lg="40" :gap-md="[16, 8]" class="mb-8">
        <v-col v-for="n in 6" :key="n" cols="12" md="4" sm="6">
          <v-sheet class="pa-3" color="primary">gap 4 → md [16, 8] → lg 40</v-sheet>
        </v-col>
      </v-row>
      <v-row class="mb-8" density="compact" gap-lg="32">
        <v-col cols="4"><v-sheet class="pa-3" color="secondary">compact → lg 32</v-sheet></v-col>
        <v-col cols="8"><v-sheet class="pa-3" color="secondary">must stay on one line</v-sheet></v-col>
      </v-row>
      <v-row gap-md="48" no-gutters>
        <v-col cols="6">
          <v-sheet class="pa-3" color="surface-variant">no-gutters → md 48</v-sheet>
          <v-row class="mt-2">
            <v-col><v-sheet class="pa-3" color="info">nested, default gap</v-sheet></v-col>
            <v-col><v-sheet class="pa-3" color="info">nested, default gap</v-sheet></v-col>
          </v-row>
        </v-col>
        <v-col cols="6"><v-sheet class="pa-3" color="surface-variant">no-gutters → md 48</v-sheet></v-col>
      </v-row>
    </v-container>
  </v-app>
</template>