Closes #13283: Add context to dropdown options

[jeremystretch]

Fixes: #13283

• Introduce support for populating the following attributes within a dropdown option:
  • Value
  • Label
  • Disabled indicator
  • Description
  • Depth in hierarchy (for indentation)
  • Parent object
• Expose a new option_attrs keyword argument on dynamic choice form fields that can be used to override default/undefined fields