feat (help): allow cli option to list tasks with no desc

added an add'l cli option that lists all tasks, with or without description.
orig. behavior: task -l lists tasks with desc field
new behaviour: task -la or task -a will list all tasks. if task has desc, it will be included.

BREAKING CHANGES: none, that I know of.
NOTES/Concerns:
- This is wip.
- Haven't checked how it interacts with bash completion.
- The new Executor.TaskNames func does not use e.CompiledTask(taskfile.Call{Task: task.Task})

task.go

@@ -64,7 +64,9 @@ func (e *Executor) Run(ctx context.Context, calls ...taskfile.Call) error {
 	for _, c := range calls {
 		if _, ok := e.Taskfile.Tasks[c.Task]; !ok {
 			// FIXME: move to the main package
-			e.PrintTasksHelp()
+			// FIXME: (ard.kevin.84@gmail.com) changed the PrintTasksHelp signature to support show all/some.
+			// 	False preserves original behavior, but should be reviewed.
+			e.PrintTasksHelp(false)
 			return &taskNotFoundError{taskName: c.Task}
 		}
 	}