fix(VBtn): prevent keyboard tab while loading

[Mohib834]

Description

When the loading prop is true, Vbtn still lets the user select the button through the tab and register the enter event.

resolves #18524

Markup:

<template>
  <v-card
    class="mx-auto"
    max-width="450"
    title="Strengthen your passwords"
    text="Update your weak or re-used passwords with Password Checkup. It's free and only takes a few minutes. Click the Take Checkup button to get started."
  >
    <template #actions>
      <v-btn height="48"> No Thanks </v-btn>

      <v-btn
        :loading="loading"
        class="flex-grow-1"
        height="48"
        variant="tonal"
        @click="load"
      >
        Take Checkup
      </v-btn>

    </template>
  </v-card>
</template>

[johnleider]

Are there any accessibility with aria attributes that we need to take into consideration?

[johnleider]

Paging @Mohib834