ejb timer timeout methods can take no arg, or one argument of type Timer.

Current WildFly ejb timer service impl processes timeout method params in a general way, assuming they can be any number of params of any types. We can simplify it knowing that the params can only be null / no-arg, or Timer.

Various places can be simplified, such as org.jboss.as.ejb3.timerservice.persistence.TimeoutMethod, serializing it before persisting it, deserialize it after retrieving from persistence.

In database, the column name for this is timeout_method_descriptor, and its value (varchar) may be
javax.ejb.Timer if it is a one-arg params.

Note: need to maintain backward compatibility with previous jboss_ejb_timer table schema, and legacy file data store.