**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
"""Returns dictionary of all global extra links"""
        from airflow import plugins_manager
        plugins_manager.initialize_extra_operators_links_plugins()
        if plugins_manager.global_operator_extra_links is None:
            raise AirflowException("Can't load operators")
        return {link.name: link for link in plugins_manager.global_operator_extra_links}
    @prepare_lineage
    def pre_execute(self, context: Any):
        """This hook is triggered right before self.execute() is called."""
        if self._pre_execute_hook is not None:
            self._pre_execute_hook(context)
    def execute(self, context: Any):
        """
        This is the main method to derive when creating an operator.
        Context is the same dictionary used as when rendering jinja templates.
        Refer to get_template_context for more context.
        """
        raise NotImplementedError()
    @apply_lineage
    def post_execute(self, context: Any, result: Any = None):
        """
        This hook is triggered right after self.execute() is called.
        It is passed the execution context and any results returned by the
        operator.
        """
        if self._post_execute_hook is not None:
            self._post_execute_hook(context, result)
    def on_kill(self) -> None: