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