`event["target"]` value for radio input and checkboxes is always `'on'`

[Archmonger]

Current Situation

The value for any serialized checkbox or radio button is always on when viewed within an event["target"]. This effectively makes them unusable within a form's on_submit event.

Proposed Actions

Fix how we serialize these input fields, and look for any other outliers that might exist.

[zx013]

If set value xxx in radio input, the value always be xxx. So I can not get which radio input I choose.