**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
from_tasks: Sequence[Union[BaseOperator, "XComArg"]],
    to_tasks: Union[BaseOperator, "XComArg", Sequence[Union[BaseOperator, "XComArg"]]],
):
    r"""
    Set downstream dependencies for all tasks in from_tasks to all tasks in to_tasks.
    Using classic operators/sensors:
    .. code-block:: python
        cross_downstream(from_tasks=[t1, t2, t3], to_tasks=[t4, t5, t6])
    is equivalent to::
        t1 ---> t4
           \ /
        t2 -X -> t5
           / \
        t3 ---> t6
    .. code-block:: python
        t1.set_downstream(t4)
        t1.set_downstream(t5)
        t1.set_downstream(t6)
        t2.set_downstream(t4)
        t2.set_downstream(t5)