Enhancements to `widget_toolkit_otp` related widgets

[DavidDWiser]

As a developer, when I am using the SmsCodeField from the widget_toolkit_otp package, I would like to have a way to reset the fields programatically or after an error occurs.
Also, I'd like to have a clear loading indication to the user when the OTP code is being processed. Current implementation handles it in such way that the input to the field is temporarily disabled (marked as read-only) until the code is validated or throws an error.

ACs:

• Update SmsCodeField and related widgets to support code reseting
  • Add an option to reset the OTP code after some time after an error occurs
  • Add an option to programatically reset the OTP code
• Add optional loading indication during the OTP code processing