**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/core/test_configuration.py
conf.deprecated_options = {
            ('logging', 'logging_level'): ('core', 'logging_level', '2.0.0'),
        }
        
        conf.remove_option('core', 'logging_level')
        conf.remove_option('logging', 'logging_level')
        with pytest.warns(DeprecationWarning):
            with mock.patch.dict('os.environ', AIRFLOW__CORE__LOGGING_LEVEL="VALUE"):
                assert conf.get('logging', 'logging_level') == "VALUE"
        with pytest.warns(DeprecationWarning), conf_vars({('core', 'logging_level'): 'VALUE'}):
            assert conf.get('logging', 'logging_level') == "VALUE"
    @conf_vars(
        {
            ("celery", "result_backend"): None,
            ("celery", "celery_result_backend"): None,
            ("celery", "celery_result_backend_cmd"): None,
        }
    )
    def test_deprecated_options_cmd(self):