fix: refactor radio group to better manage disabled state and interactions

[chrisdholt]

Pull Request

📖 Description

This PR proposes a slight refactor of radio group in order to support the disabling of the radiogroup without modifying the state of individual radio children. This PR does a few things:

1. Removes click handling behavior for the radio itself and manages via the group. Per the APG, radios which are not selected (primarily on page-load scenarios) can be selected via "Space" so that behavior remains in tact.

2. Removes behavior modifying each disabled items disabled state. For the sake of ensuring we don't break with future changes to the disabledChanged method, I've left this enumerated as protected for now.

3. Assigns a tabindex of -1 to prevent focus from being brought to the element and its children.

4. To ensure that focus does not pass to the radiogroup when clicked, a mousedown event has been added to prevent focus when disabled.

🎫 Issues

fixes #6567

👩‍💻 Reviewer Notes

📑 Test Plan

Tests have been added for most all pertinent scenarios

✅ Checklist

General

• I have included a change request file using $ yarn change
• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

Component-specific

• I have added a new component
• I have modified an existing component
• I have updated the definition file
• I have updated the configuration file

⏭ Next Steps

[radium-v]

radio-group has some special interaction behaviors when in a toolbar, so it'd be good to just double-check that everything here works in that scenario as well (it probably does).