**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
from airflow.models.param import DagParam
        from airflow.models.xcom_arg import XComArg
        if isinstance(content, str):
            if any(content.endswith(ext) for ext in self.template_ext):
                
                return jinja_env.get_template(content).render(**context)
            else:
                return jinja_env.from_string(content).render(**context)
        elif isinstance(content, (XComArg, DagParam)):
            return content.resolve(context)
        if isinstance(content, tuple):
            if type(content) is not tuple:
                
                return content.__class__(
                    *(self.render_template(element, context, jinja_env) for element in content)
                )
            else:
                return tuple(self.render_template(element, context, jinja_env) for element in content)
        elif isinstance(content, list):
            return [self.render_template(element, context, jinja_env) for element in content]
        elif isinstance(content, dict):
            return {key: self.render_template(value, context, jinja_env) for key, value in content.items()}
        elif isinstance(content, set):
            return {self.render_template(element, context, jinja_env) for element in content}
        else:
            if seen_oids is None:
                seen_oids = set()
            self._render_nested_template_fields(content, context, jinja_env, seen_oids)
            return content
    def _render_nested_template_fields(