**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
tr=weight_rule,
                )
            )
        self.weight_rule = weight_rule
        self.resources: Optional[Resources] = Resources(**resources) if resources else None
        self.run_as_user = run_as_user
        if task_concurrency and not max_active_tis_per_dag:
            
            warnings.warn(
                "The 'task_concurrency' parameter is deprecated. Please use 'max_active_tis_per_dag'.",
                DeprecationWarning,
                stacklevel=2,
            )
            max_active_tis_per_dag = task_concurrency
        self.max_active_tis_per_dag = max_active_tis_per_dag
        self.executor_config = executor_config or {}
        self.do_xcom_push = do_xcom_push
        self.doc_md = doc_md
        self.doc_json = doc_json
        self.doc_yaml = doc_yaml
        self.doc_rst = doc_rst
        self.doc = doc
        
        self._upstream_task_ids: Set[str] = set()
        self._downstream_task_ids: Set[str] = set()
        self._dag = None
        self.dag = dag or DagContext.get_current_dag()
        
        
        from airflow.models.dag import DAG