**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
"""@property: list of tasks directly upstream"""
        return [self.dag.get_task(tid) for tid in self._upstream_task_ids]
    @property
    def upstream_task_ids(self) -> Set[str]:
        """@property: set of ids of tasks directly upstream"""
        return self._upstream_task_ids
    @property
    def downstream_list(self) -> List["BaseOperator"]:
        """@property: list of tasks directly downstream"""
        return [self.dag.get_task(tid) for tid in self._downstream_task_ids]
    @property
    def downstream_task_ids(self) -> Set[str]:
        """@property: set of ids of tasks directly downstream"""
        return self._downstream_task_ids
    @provide_session
    def clear(