**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/models/baseoperator.py
that is visible in Task Instance details View in the Webserver
    :type doc_rst: str
    :param doc_json: Add documentation (in JSON format) or notes to your Task objects
        that is visible in Task Instance details View in the Webserver
    :type doc_json: str
    :param doc_yaml: Add documentation (in YAML format) or notes to your Task objects
        that is visible in Task Instance details View in the Webserver
    :type doc_yaml: str
    """
    
    template_fields: Iterable[str] = ()
    
    template_ext: Iterable[str] = ()
    
    template_fields_renderers: Dict[str, str] = {}
    
    ui_color = '#fff'  
    ui_fgcolor = '#000'  
    pool = ""  
    
    _base_operator_shallow_copy_attrs: Tuple[str, ...] = (
        'user_defined_macros',
        'user_defined_filters',
        'params',
        '_log',
    )
    
    shallow_copy_attrs: Tuple[str, ...] = ()
    
    operator_extra_links: Iterable['BaseOperatorLink'] = ()