enh: remove wrapping element from detachable components

[KaelWD]

Description

Blocked by vuejs/vue#8350, only works with vue <2.5.16

Motivation and Context

fixes #3205, fixes #3107

How Has This Been Tested?

Markup:

<template>
  <v-app>
    <v-container>
      <v-card dark>
        <v-card-text>
          <v-dialog>
            <v-btn slot="activator">dialog 1</v-btn>
            <v-card>
              <v-card-text>
                Dialog 1
              </v-card-text>
            </v-card>
          </v-dialog>
          <v-text-field v-model="text"/>
          <v-dialog>
            <v-btn slot="activator">dialog 2</v-btn>
            <v-card>
              <v-card-text>
                Dialog 2
              </v-card-text>
            </v-card>
          </v-dialog>
        </v-card-text>
      </v-card>
    </v-container>
  </v-app>
</template>

<script>
  export default {
    data: () => ({
      text: ''
    })
  }
</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 feature but make things better)

Checklist:

• My change requires a change to the documentation.
• I have created a PR in the documentation with the necessary changes.

[codecov]

Codecov Report

Merging #3206 into dev will increase coverage by 0.29%.
The diff coverage is 67.24%.

@@            Coverage Diff             @@
##              dev    #3206      +/-   ##
==========================================
+ Coverage   88.89%   89.19%   +0.29%     
==========================================
  Files         227      207      -20     
  Lines        5376     4866     -510     
  Branches     1360     1225     -135     
==========================================
- Hits         4779     4340     -439     
+ Misses        479      420      -59     
+ Partials      118      106      -12

Impacted Files	Coverage Δ
src/components/VDialog/VDialogContent.js	64.44% <64.44%> (ø)
src/components/VDialog/VDialog.js	78.57% <76.92%> (+7.14%)	⬆️
src/mixins/dependent.js	54.16% <0%> (-45.84%)	⬇️
src/components/VMenu/mixins/menu-activator.js	44.44% <0%> (-3.71%)	⬇️
src/components/VForm/VForm.js	83.78% <0%> (-3.18%)	⬇️
src/components/VOverflowBtn/VOverflowBtn.js	91.42% <0%> (-3.17%)	⬇️
src/components/VDataTable/VEditDialog.js	20% <0%> (-2.59%)	⬇️
src/mixins/menuable.js	93.13% <0%> (-2.01%)	⬇️
src/mixins/validatable.js	91.8% <0%> (-1.85%)	⬇️
src/mixins/selectable.js	93.87% <0%> (-1.58%)	⬇️
... and 202 more

---

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[IPRIT]

Do you know that u can't import functional components as Async Component (e.g. VDivider => import('path/to/VDivider.vue')). Server Renderer throw an error because component has no componentOptions and Ctor object.

[KaelWD]

That was fixed in 2.5.16: vuejs/vue#7784

[johnleider]

Re-open when this is seeing progress again.