Do not use 'RADIO_SIZE 20' as the fixed width of the radio button, but use the actual width as returned by wxRendererNative. wxRendererNative has no GetRadioButtonSize, so for now use GetCheckBoxSize. It returns the same sizes. Also add a half character width to account for the space between the button and the label. There is no need to add extra width to the label of the static box. Closes #18010.