Add prompt when --secret is missing for Mask command.

Use case:
User have automation script using wildfly elytron tool and user don't want to have secret value stored in file.
User don't want secret value to be stored in shell history after execution.
User don't want secret value to be listed in ps -aux output.

There have to be possibility to omit --secret. When omitting --secret attribute user interaction prompt should follow with possibility to input secret value.

How to reproduce

java -jar wildfly-elytron-tool.jar mask -i 240 -s 12345678