**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
doc_md: Optional[str] = None,
        doc_json: Optional[str] = None,
        doc_yaml: Optional[str] = None,
        doc_rst: Optional[str] = None,
        **kwargs,
    ):
        from airflow.models.dag import DagContext
        from airflow.utils.task_group import TaskGroupContext
        super().__init__()
        if kwargs:
            if not conf.getboolean('operators', 'ALLOW_ILLEGAL_ARGUMENTS'):
                raise AirflowException(
                    "Invalid arguments were passed to {c} (task_id: {t}). Invalid "
                    "arguments were:\n**kwargs: {k}".format(c=self.__class__.__name__, k=kwargs, t=task_id),
                )
            warnings.warn(
                'Invalid arguments were passed to {c} (task_id: {t}). '
                'Support for passing such arguments will be dropped in '
                'future. Invalid arguments were:'
                '\n**kwargs: {k}'.format(c=self.__class__.__name__, k=kwargs, t=task_id),
                category=PendingDeprecationWarning,
                stacklevel=3,
            )
        validate_key(task_id)
        self.task_id = task_id
        self.label = task_id
        task_group = task_group or TaskGroupContext.get_current_task_group(dag)
        if task_group:
            self.task_id = task_group.child_id(task_id)
            task_group.add(self)