lang: core, funcs: Port some functions to CallableFunc API

Some modern features of our function engine and language might require
this new API, so port what we can and figure out the rest later.

lang/core/world/schedule.go

@@ -88,6 +88,8 @@ type ScheduleFunc struct {
 
 	init *interfaces.Init
 
+	args []types.Value
+
 	namespace string
 	scheduler *scheduler.Result
 
@@ -303,7 +305,15 @@ func (obj *ScheduleFunc) Stream(ctx context.Context) error {
 			}
 			obj.last = input // store for next
 
-			namespace := input.Struct()[scheduleArgNameNamespace].Str()
+			args, err := interfaces.StructToCallableArgs(input) // []types.Value, error)
+			if err != nil {
+				return err
+			}
+			obj.args = args
+
+			namespace := args[0].Str()
+
+			//namespace := input.Struct()[scheduleArgNameNamespace].Str()
 			if namespace == "" {
 				return fmt.Errorf("can't use an empty namespace")
 			}