Align signatures of ad-hoc and scheduled task CLI scripts

The following CLI scripts exist:

• `admin/tool/task/cli/adhoc_task.php`
• `admin/tool/task/cli/schedule_task.php`

These scripts allow for various processing of tasks in Moodle. However, they have different signatures and allow different functionality. The functionality of these scripts should be more fully aligned.

For `admin/tool/task/cli/adhoc_task.php` the following options should be added

• `--execute="\some\adhoc\task\class"` Execute all adhoc tasks of particular task
• `--list` list basic tabularised data of pending adhoc tasks (class, creation date, userid)

For `admin/tool/task/cli/schedule_task.php` the following option should be added

• `-execute` or `-execute="*"` execute all scheduled tasks

Adding an execute all function will also allow for schedule tasks and ad-hoc tasks to be executed independently on individual nodes.

Because of the differences between the two sorts of tasks we can't fully align them. But this improvement is still worth while