**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
:type include_env: bool
        :param include_cmds: Should the result of calling any *_cmd config be
            set (True, default), or should the _cmd options be left as the
            command to run (False)
        :type include_cmds: bool
        :param include_secret: Should the result of calling any *_secret config be
            set (True, default), or should the _secret options be left as the
            path to get the secret from (False)
        :type include_secret: bool
        :rtype: Dict[str, Dict[str, str]]
        :return: Dictionary, where the key is the name of the section and the content is
            the dictionary with the name of the parameter and its value.
        """
        config_sources: Dict[str, Dict[str, str]] = {}
        configs = [
            ('default', self.airflow_defaults),
            ('airflow.cfg', self),
        ]
        self._replace_config_with_display_sources(config_sources, configs, display_source, raw)
        
        if include_env:
            self._include_envs(config_sources, display_sensitive, display_source, raw)
        
        if include_cmds:
            self._include_commands(config_sources, display_sensitive, display_source, raw)
        
        if include_secret:
            self._include_secrets(config_sources, display_sensitive, display_source, raw)
        return config_sources
    def _include_secrets(self, config_sources, display_sensitive, display_source, raw):