This commit changes the method prepareTaskStrategy() in the class
SimpleWorker and all its child classes to use ScheduledTaskEntity
instead of ScheduledTask.
[MAILPOET-2996]
This commit adds a helper method called convertTaskClass() to
CronWorkerRunner to support the migration of the code inside this class
from Paris to Doctrine. This method receives a ScheduledTaskEntity and
returns a ScheduledTask. It will be remove once the migration is
finished.
[MAILPOET-2996]
