feat(theme): add anchor color support

[johnleider]

resolves #6360

Description

Added the ability to define an application's anchor color

Motivation and Context

Currently, the anchor color is defined as the application's primary color which may not always be desired

How Has This Been Tested?

jest

Markup:

// Paste your FULL Playground.vue here
// dev/index.js

const vuetify = new Vuetify({
  theme: {
    themes: {
      options: {
        // customProperties: true,
      },
      light: {
        anchor: '#000'
      }
    }
  },
  lang: {
    locales,
  },
})

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:

• 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 breaking 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)

[codecov]

Codecov Report

Merging #7455 into next will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##             next    #7455      +/-   ##
==========================================
+ Coverage   87.17%   87.19%   +0.02%     
==========================================
  Files         326      326              
  Lines        8447     8453       +6     
  Branches     2116     2120       +4     
==========================================
+ Hits         7364     7371       +7     
+ Misses        993      992       -1     
  Partials       90       90

Impacted Files	Coverage Δ
packages/vuetify/src/services/theme/utils.ts	100% <100%> (ø)	⬆️
packages/vuetify/src/components/VSelect/VSelect.ts	94.42% <0%> (+0.42%)	⬆️

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