[Technical] Rename the class of the task manager application to TaskClass instead of TaskManagerClass

Today the class of the application is called TaskManagerClass, following the naming convention of AWM, as this application was started as an App Within Minutes.

In order to have some coherence, the class should be called TaskClass.
Since this would involve a class rename (which requires handling the migration of existing objects of the class), this can be done along with TASKMAN-54 (which involves the same class rename).