Improve RadioButton Click event implementation

[Descolada]

RadioButton is documented to have a Click event, but it apparently wasn't wired up on platforms other than macOS.

Expected behavior: triggers once on every click on the radio button, even if it's already checked.

• WinForms: tested, but for unknown reasons the event triggers twice (I could not determine the reason in a reasonable timeframe and gave up on it)
• Wpf: tested, working
• Gtk: tested, working
• iOS: not tested
• macOS: not tested (existing handler unchanged)
• Android: not tested

[cwensley]

This looks great! Thanks for the fixes. 🙏

I've added a fix for WinForms so it doesn't trigger twice, looks like the control styles were causing that, but I've verified with them off it still behaves correctly.