**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

airflow/configuration.py
"""Historical load_test_config"""
    warnings.warn(
        "Accessing configuration method 'load_test_config' directly from the configuration module is "
        "deprecated. Please access the configuration from the 'configuration.conf' object via "
        "'conf.load_test_config'",
        DeprecationWarning,
        stacklevel=2,
    )
    conf.load_test_config()
def get(*args, **kwargs):
    """Historical get"""
    warnings.warn(
        "Accessing configuration method 'get' directly from the configuration module is "
        "deprecated. Please access the configuration from the 'configuration.conf' object via "
        "'conf.get'",
        DeprecationWarning,
        stacklevel=2,
    )
    return conf.get(*args, **kwargs)
def getboolean(*args, **kwargs):