**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

tests/models/test_baseoperator.py
"""Class for testing purpose: allows to create objects with custom attributes in one single statement."""
    def __init__(self, **kwargs):
        for key, value in kwargs.items():
            setattr(self, key, value)
    def __str__(self):
        return f"{ClassWithCustomAttributes.__name__}({str(self.__dict__)})"
    def __repr__(self):
        return self.__str__()
    def __eq__(self, other):
        return self.__dict__ == other.__dict__
    def __ne__(self, other):
        return not self.__eq__(other)
object1 = ClassWithCustomAttributes(attr="{{ foo }}_1", template_fields=["ref"])
object2 = ClassWithCustomAttributes(attr="{{ foo }}_2", ref=object1, template_fields=["ref"])
setattr(object1, 'ref', object2)
class DummyClass(metaclass=BaseOperatorMeta):