**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
"'{d}.{t}'; received '{tr}'.".format(
                    all_triggers=TriggerRule.all_triggers(),
                    d=dag.dag_id if dag else "",
                    t=task_id,
                    tr=trigger_rule,
                )
            )
        self.trigger_rule = trigger_rule
        self.depends_on_past = depends_on_past
        self.wait_for_downstream = wait_for_downstream
        if wait_for_downstream:
            self.depends_on_past = True
        if retries is not None and not isinstance(retries, int):
            try:
                parsed_retries = int(retries)
            except (TypeError, ValueError):
                raise AirflowException(f"'retries' type must be int, not {type(retries).__name__}")
            self.log.warning("Implicitly converting 'retries' for %s from %r to int", self, retries)
            retries = parsed_retries
        self.retries = retries
        self.queue = queue
        self.pool = Pool.DEFAULT_POOL_NAME if pool is None else pool
        self.pool_slots = pool_slots
        if self.pool_slots < 1:
            raise AirflowException(f"pool slots for {self.task_id} in dag {dag.dag_id} cannot be less than 1")
        self.sla = sla
        self.execution_timeout = execution_timeout
        self.on_execute_callback = on_execute_callback
        self.on_failure_callback = on_failure_callback
        self.on_success_callback = on_success_callback