**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
with DAG(dag_id='xcomargs_test', default_args={"start_date": datetime.today()}):
            op1 = BaseOperator(task_id="op1")
            op2 = MockOperator(task_id="op2")
            op2.arg1 = op1.output  
        assert op1 in op2.upstream_list
    def test_set_xcomargs_dependencies_error_when_outside_dag(self):
        with pytest.raises(AirflowException):
            op1 = BaseOperator(task_id="op1")
            MockOperator(task_id="op2", arg1=op1.output)
    def test_invalid_trigger_rule(self):
        with pytest.raises(
            AirflowException,
            match=(
                f"The trigger_rule must be one of {TriggerRule.all_triggers()},"
                "'.op1'; received 'some_rule'."
            ),
        ):
            BaseOperator(task_id="op1", trigger_rule="some_rule")
    @pytest.mark.parametrize(("rule"), [("dummy"), (TriggerRule.DUMMY)])
    def test_replace_dummy_trigger_rule(self, rule):
        with pytest.warns(
            DeprecationWarning, match="dummy Trigger Rule is deprecated. Please use `TriggerRule.ALWAYS`."
        ):
            op1 = BaseOperator(task_id="op1", trigger_rule=rule)
            assert op1.trigger_rule == TriggerRule.ALWAYS
def test_init_subclass_args():
    class InitSubclassOp(BaseOperator):