Fix/menu position

[johnleider]

Description

Update how calculations are derived for menu

Motivation and Context

Fix inconsistencies in various use-cases
fixes #5498

How Has This Been Tested?

jest

Markup:

```vue // Paste your FULL Playground.vue here

All arrow_drop_down

      <v-list>
        <v-list-tile
          v-for="item in items"
          :key="item"
          @click=""
        >
          <v-list-tile-title v-text="item"></v-list-tile-title>
        </v-list-tile>
      </v-list>
    </v-menu>


    <v-menu offset-y :max-width="500" :min-width="200">
      <v-btn
             slot="activator"
             color="primary"
             dark>
        Test
      </v-btn>
      <v-list>
        <v-list-tile
                     v-for="(item, index) in items2"
                     :key="index"
                     @click=""
                     >
          <v-list-tile-title>{{ item.title }}</v-list-tile-title>
        </v-list-tile>
      </v-list>
    </v-menu>

    <v-btn icon>
      <v-icon>search</v-icon>
    </v-btn>

    <v-btn icon>
      <v-icon>favorite</v-icon>
    </v-btn>

    <v-btn icon>
      <v-icon>more_vert</v-icon>
    </v-btn>
  </v-toolbar>
</v-card>

<script> export default { data: () => ({ items: [ 'All', 'Family', 'Friends', 'Coworkers' ], items2: [ { title: 'test' }, { title: 'Click Me' }, { title: 'Click Me' }, { title: 'Click Me 2' } ] }) } </script>

</details>

## Types of changes
<!--- What types of changes does your code introduce? Put an `x` in all the boxes that apply: -->
- [x] 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:
<!--- Go over all the following points, and put an `x` in all the boxes that apply. -->
<!--- If you're unsure about any of these, don't hesitate to ask. We're here to help! -->
- [x] The PR title is no longer than 64 characters.
- [x] The PR is submitted to the correct branch (`master` for bug fixes and documentation updates, `dev` for new features and breaking changes).
- [x] 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) 

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[codecov]

Codecov Report

Merging #6193 into master will increase coverage by 0.05%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #6193      +/-   ##
==========================================
+ Coverage   89.48%   89.53%   +0.05%     
==========================================
  Files         276      276              
  Lines        6316     6318       +2     
  Branches     1593     1594       +1     
==========================================
+ Hits         5652     5657       +5     
+ Misses        545      542       -3     
  Partials      119      119

Impacted Files	Coverage Δ
packages/vuetify/src/components/VMenu/VMenu.js	83.63% <ø> (ø)	⬆️
packages/vuetify/src/mixins/menuable.js	91.93% <100%> (+0.13%)	⬆️
...fy/src/components/transitions/expand-transition.js	72% <0%> (+12%)	⬆️

---

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[lock]

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