"focus" handling for RadioGroup

[giogonzo]

Project card

requirements

Same as we did in #1288 for Checkbox and Toggle:

• Unlike other form fields, RadioGroup currently doesn't have onFocus/onBlur props
• If interacting with the form through a keyboard, RadioGroup doesn't display any meaningful "focus" indication
• it should also be possible to change RadioGroup value via a keyboard

specs

{optional: describe technical specs to implement this feature, if not obvious}

misc

{optional: other useful info}