**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
def __init__(self, test_param, params=None, default_args=None):
        self.test_param = test_param
    def set_xcomargs_dependencies(self):
        ...
class DummySubClass(DummyClass):
    def __init__(self, test_sub_param, **kwargs):
        super().__init__(**kwargs)
        self.test_sub_param = test_sub_param
class TestBaseOperator:
    def test_apply(self):
        dummy = DummyClass(test_param=True)
        assert dummy.test_param
        with pytest.raises(AirflowException, match='Argument.*test_param.*required'):
            DummySubClass(test_sub_param=True)
    def test_default_args(self):
        default_args = {'test_param': True}
        dummy_class = DummyClass(default_args=default_args)
        assert dummy_class.test_param
        default_args = {'test_param': True, 'test_sub_param': True}
        dummy_subclass = DummySubClass(default_args=default_args)
        assert dummy_class.test_param
        assert dummy_subclass.test_sub_param
        default_args = {'test_param': True}
        dummy_subclass = DummySubClass(default_args=default_args, test_sub_param=True)
        assert dummy_class.test_param
        assert dummy_subclass.test_sub_param
        with pytest.raises(AirflowException, match='Argument.*test_sub_param.*required'):
            DummySubClass(default_args=default_args)
    def test_incorrect_default_args(self):