**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 getsection"""
    warnings.warn(
        "Accessing configuration method 'getsection' directly from the configuration module is "
        "deprecated. Please access the configuration from the 'configuration.conf' object via "
        "'conf.getsection'",
        DeprecationWarning,
        stacklevel=2,
    )
    return conf.getsection(*args, **kwargs)
def has_option(*args, **kwargs):
    """Historical has_option"""
    warnings.warn(
        "Accessing configuration method 'has_option' directly from the configuration module is "
        "deprecated. Please access the configuration from the 'configuration.conf' object via "
        "'conf.has_option'",
        DeprecationWarning,
        stacklevel=2,
    )
    return conf.has_option(*args, **kwargs)
def remove_option(*args, **kwargs):
    """Historical remove_option"""
    warnings.warn(
        "Accessing configuration method 'remove_option' directly from the configuration module is "
        "deprecated. Please access the configuration from the 'configuration.conf' object via "
        "'conf.remove_option'",
        DeprecationWarning,
        stacklevel=2,
    )
    return conf.remove_option(*args, **kwargs)
def as_dict(*args, **kwargs):