fix(VItem): support disabled effect

[yuwu9145]

fixes #14923

Description

fixes #14923

Motivation and Context

How Has This Been Tested?

visually

Markup:

// Paste your FULL Playground.vue here
<template>
  <v-container>
    <v-item-group>
      <v-container>
        <v-row>
          <v-col
            v-for="n in 3"
            :key="n"
            cols="12"
            md="4"
          >
            <v-item 
                v-slot="{ active, toggle }"
                disabled
            >

              <v-card
                :color="active ? 'primary' : ''"
                class="d-flex align-center"
                dark
                height="200"
                @click="toggle"
              >
               <v-badge overlap>
                <template v-slot:badge>
                  <v-icon>mdi-magnify</v-icon>
                 </template>
                <v-icon>mdi-clipboard</v-icon>
              </v-badge> 
                  <v-scroll-y-transition>
                  <div
                    v-if="active"
                    class="text-h2 flex-grow-1 text-center"
                  >
                    Active
                  </div>
                </v-scroll-y-transition>
              </v-card>
            </v-item>
          </v-col>
        </v-row>

      </v-container>
    </v-item-group> 
      <!--  -->
  </v-container>
</template>

<script>
  export default {
    data: () => ({
    //
    }),
  }
</script>

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Improvement/refactoring (non-breaking change that doesn't add any features but makes things better)

Checklist:

• The PR title is no longer than 64 characters.
• The PR is submitted to the correct branch (master for bug fixes and documentation updates, dev for new features and backwards compatible changes and next for non-backwards compatible changes).
• My code follows the code style of this project.
• I've added relevant changes to the documentation (applies to new features and breaking changes in core library)

[KaelWD]

Disabled items can still be tabbed to and activated with the keyboard, see #14229 and #14606.

[yuwu9145]

@KaelWD Thanks for the hints, pull request has been updated to cover both issues. In addition, playground markup code has been updated as well to simulate tab & click event from child elements