**Description**

It would be nice if the weight_rule default value could be managed by a global config

suggested config:
```
# Weighting method used for the effective total priority weight of the task. 
# Options are: { downstream | upstream | absolute } default is
default_weight_rule = downstream
```
**Use case / motivation**

In some pipeline, you really need to have absolute weight, and then you have to add a line in each task definition which is annoying

airflow/models/baseoperator.py
self,
        task_or_task_list: Union[TaskMixin, Sequence[TaskMixin]],
        edge_modifier: Optional[EdgeModifier] = None,
    ) -> None:
        """
        Set a task or a task list to be directly downstream from the current
        task. Required by TaskMixin.
        """
        self._set_relatives(task_or_task_list, upstream=False, edge_modifier=edge_modifier)
    def set_upstream(
        self,
        task_or_task_list: Union[TaskMixin, Sequence[TaskMixin]],
        edge_modifier: Optional[EdgeModifier] = None,
    ) -> None:
        """
        Set a task or a task list to be directly upstream from the current
        task. Required by TaskMixin.
        """
        self._set_relatives(task_or_task_list, upstream=True, edge_modifier=edge_modifier)
    @property
    def output(self):