**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 = {
            ('celery', 'worker_concurrency'): ('celery', 'celeryd_concurrency', '2.0.0'),
        }
        
        conf.remove_option('celery', 'worker_concurrency')
        with pytest.warns(DeprecationWarning):
            with mock.patch.dict('os.environ', AIRFLOW__CELERY__CELERYD_CONCURRENCY="99"):
                assert conf.getint('celery', 'worker_concurrency') == 99
        with pytest.warns(DeprecationWarning), conf_vars({('celery', 'celeryd_concurrency'): '99'}):
            assert conf.getint('celery', 'worker_concurrency') == 99
    @conf_vars(
        {
            ('logging', 'logging_level'): None,
            ('core', 'logging_level'): None,
        }
    )
    def test_deprecated_options_with_new_section(self):