**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
__serialized_fields: Optional[FrozenSet[str]] = None
    _comps = {
        'task_id',
        'dag_id',
        'owner',
        'email',
        'email_on_retry',
        'retry_delay',
        'retry_exponential_backoff',
        'max_retry_delay',
        'start_date',
        'depends_on_past',
        'wait_for_downstream',
        'priority_weight',
        'sla',
        'execution_timeout',
        'on_execute_callback',
        'on_failure_callback',
        'on_success_callback',
        'on_retry_callback',
        'do_xcom_push',
    }
    
    supports_lineage = False
    
    __instantiated = False
    
    _lock_for_execution = False
    def __init__(